JP7709610B2 - Electrode assembly, battery, battery pack including same, and automobile - Google Patents

Description

The present invention relates to an electrode assembly, a battery, a battery pack including the same, and an automobile.

This application claims priority to Korean Patent Application No. 10-2021-0160823 filed on November 19, 2021, and Korean Patent Application No. 10-2022-0005393 filed on January 13, 2022, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings.

Secondary batteries, which have high applicability to each product group and electrical properties such as high energy density, are commonly used not only in portable devices but also in electric vehicles (EVs) and hybrid electric vehicles (HEVs) that are driven by electrical sources.

Such secondary batteries not only have the primary advantage of dramatically reducing the use of fossil fuels, but are also environmentally friendly as they do not produce any by-products from energy use, and are garnering attention as a new energy source for improving energy efficiency.

Currently, secondary batteries such as lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel metal hydride batteries, and nickel zinc batteries are widely used. The operating voltage of such unit secondary batteries, i.e., unit batteries, is approximately 2.5V to 4.5V. Therefore, when a higher output voltage is required, a battery pack is formed by connecting multiple batteries in series. In addition, a battery pack may be formed by connecting multiple batteries in parallel according to the charge/discharge capacity required for the battery pack. Therefore, the number of batteries included in the battery pack and the electrical connection form can be variously set according to the required output voltage and/or charge/discharge capacity.

Meanwhile, known types of unit secondary batteries include cylindrical, prismatic and pouch-type batteries. In the case of a cylindrical battery, a separator, which is an insulator, is interposed between the positive and negative electrodes, and the separator is wound up to form a jelly-roll-type electrode assembly, which is then inserted into a battery housing to form a battery. The battery housing is called a battery can in the industry. Strip-shaped electrode tabs are connected to the uncoated portions of the positive and negative electrodes, and the electrode tabs electrically connect the electrode assembly to the electrode terminals exposed to the outside. For reference, the positive terminal is a sealed cap that seals the opening of the battery housing, and the negative terminal is the battery housing. However, in a conventional cylindrical battery having such a structure, current is concentrated in the strip-shaped electrode tabs connected to the positive and/or negative uncoated portions, resulting in high resistance, high heat generation and poor current collection efficiency.

In small cylindrical batteries with form factors of 1865 (diameter: 18 mm, height: 65 mm) or 2170 (diameter: 21 mm, height: 70 mm), resistance and heat generation are not a major issue. However, when the form factor of a cylindrical battery is increased to be used in an electric vehicle, a large amount of heat is generated around the electrode tabs during the fast charging process, which can cause the cylindrical battery to catch fire.

To solve this problem, a cylindrical battery (a so-called tab-less cylindrical battery) has been proposed, which is designed so that positive and negative uncoated areas are located at the top and bottom of the jelly-roll type electrode assembly, respectively, and current collectors are welded to these uncoated areas to improve current collection efficiency.

Figures 1 to 3 show the manufacturing process of a tabless cylindrical battery. Figure 1 shows the structure of the electrode, Figure 2 shows the electrode winding process, and Figure 3 shows the process of welding the current collector to the folded surface area of the uncoated part.

Referring to Figures 1 to 3, the positive electrode 10 and the negative electrode 11 have a structure in which an active material 21 is coated on a sheet-shaped current collector 20, and include a plain area 22 on one long side along the winding direction (X-axis). The long side refers to the side that is parallel to the X-axis direction and has a relatively long length.

Electrode assembly A is manufactured by stacking the positive electrode 10 and the negative electrode 11 together with two separators 12 in order as shown in FIG. 2, and then winding them up in one direction (X-axis direction). At this time, the uncoated portion of the positive electrode 10 and the uncoated portion of the negative electrode 11 are arranged in opposite directions.

After the winding process, the uncoated portion 10a of the positive electrode 10 and the uncoated portion 11a of the negative electrode 11 are folded toward the core. Then, the current collectors 30 and 31 are welded to the uncoated portions 10a and 11a, respectively.

The positive electrode uncoated area 10a and the negative electrode uncoated area 11a do not have separate electrode tabs attached, and the current collectors 30 and 31 are connected to external electrode terminals, and the current path is formed with a large cross-sectional area along the winding axis direction of the electrode assembly A (see arrow), which has the advantage of reducing the resistance of the battery. This is because resistance is inversely proportional to the cross-sectional area of the path through which the current flows.

In a tabless cylindrical battery, in order to improve the welding characteristics between the uncoated portions 10a, 11a and the current collectors 30, 31, strong pressure must be applied to the welding areas of the uncoated portions 10a, 11a to bend them as flat as possible.

However, when the welded areas of the uncoated portions 10a and 11a are bent, the patterns of the uncoated portions 10a and 11a may be deformed and distorted irregularly. In this case, the deformed portion may come into contact with an electrode of the opposite polarity, causing an internal short circuit, or may induce fine cracks in the uncoated portions 10a and 11a. In addition, the uncoated portion 32 adjacent to the core of the electrode assembly A is bent, blocking all or a significant portion of the cavity 33 in the core of the electrode assembly A. In this case, a problem occurs in the electrolyte injection process. That is, the cavity 33 in the core of the electrode assembly A is used as a passage through which the electrolyte is injected. However, if the passage is blocked, it is difficult to inject the electrolyte. In addition, when the electrolyte injector is inserted into the cavity 33, interference with the uncoated portion 32 near the core may occur, causing the uncoated portion 32 to break.

In addition, the bent portions of the plain areas 10a, 11a where the current collectors 30, 31 are welded must overlap in multiple places and must not have any open spaces (gaps). This ensures sufficient welding strength and prevents the laser from penetrating into the electrode assembly A and melting the separator or active material when using the latest technology such as laser welding.

On the other hand, in the folded surface area formed by folding the uncoated portions 10a, 11a of the electrode assembly A, there are almost no gaps through which the electrolyte can pass in the winding axis direction. This is because the gaps between the winding turns that existed immediately after winding are almost eliminated in the process of folding the uncoated portions 10a, 11a. Therefore, in a structure in which the entire ends of the uncoated portions 10a, 11a are folded, the electrolyte impregnation time may be increased.

In addition, in a conventional table-less cylindrical battery, a positive electrode uncoated area 10a is formed on the entire upper side of the electrode assembly A. Therefore, when the outer peripheral surface of the upper end of the battery housing is pressed inward to form a beading portion, the peripheral area 34 of the upper end of the electrode assembly A is compressed by the battery housing. Such compression partially deforms the electrode assembly A, and at this time, the separator 12 may break, causing an internal short circuit. If a short circuit occurs inside the battery, it may lead to heat generation or explosion of the battery.

The present invention was devised against the background of the above-mentioned conventional technology, and has as its object to provide an electrode assembly having an improved uncoated portion structure that can reduce the stress applied to the uncoated portions when the uncoated portions exposed at both ends of the electrode assembly are folded.

Another object of the present invention is to provide an electrode assembly in which the electrolyte injection passage is not blocked even if the uncoated portion is folded.

Another object of the present invention is to provide an electrode assembly that includes a structure that can prevent the upper edge of the electrode assembly from coming into contact with the inner surface of the battery housing when the upper end of the battery housing is beaded.

Another object of the present invention is to provide an electrode assembly that improves the physical properties of the welding area by applying a segment structure to the uncoated portion of the electrode and optimizing the dimensions of the segments (width, height, and spacing pitch) to sufficiently increase the number of segments stacked in the area used as the welding target area.

Another object of the present invention is to provide an electrode assembly with improved energy density and reduced resistance by applying a structure in which a current collector is welded over a wide area to the folded surface area formed by bending the segments.

Another object of the present invention is to provide an electrode assembly having a structure that allows the current collector to be stably welded to the electrode assembly.

Another object of the present invention is to provide an electrode assembly with improved electrolyte impregnation characteristics.

Another object of the present invention is to provide a battery that includes terminals and current collectors with improved designs that allow electrical wiring to be performed at the top.

Another object of the present invention is to provide a battery including an electrode assembly having an improved structure, a battery pack including the battery, and a vehicle including the battery pack.

The technical problems that the present invention aims to solve are not limited to those described above, and other problems will be clearly understood by those of ordinary skill in the art from the following description of the invention.

To achieve the above object, an electrode assembly according to one aspect of the present invention is an electrode assembly in which a core and an outer circumferential surface are defined by winding a first electrode, a second electrode, and a separator interposed between the first electrode and the second electrode around a winding shaft, and at least one of the first electrode and the second electrode includes an active material portion coated with an active material layer along the winding direction, and a plain portion not coated with the active material layer.

At least a portion of the uncoated portion may itself be used as an electrode tab.

The uncoated portion may include an insulating layer formed along the winding direction at the base end, which is the boundary region with the active material layer.

The plain portion may include a section that is divided into a plurality of segments that can be bent independently by a plurality of cutting grooves provided along the winding direction.

The gap between the bottom of the cutting groove and the insulating layer may vary along the winding direction.

When the segment is bent, the insulating layer supports the base end of the uncoated portion, thereby preventing deformation of the base end of the uncoated portion. Since the rigidity of the base end is reinforced, the segment can be bent accurately based on the bottom end of the segment.

At least a portion of the insulating layer may be exposed to the outside of the separation membrane. By covering the uncoated portion that protrudes outward from the separation membrane when the divided piece is folded with an insulating layer, it is possible to prevent a short circuit from occurring between adjacent electrodes of different polarities.

The insulating layer formed on the uncoated portion may be thinner than the active material layer and may be disposed at a distance from the separator. That is, the active material layer may be in contact with the separator, while there may be a gap between the insulating layer on the uncoated portion and the separator. As a result, even if the base end of the uncoated portion is deformed to some extent due to the bending force when the divided piece is bent, the insulating layer can minimize the effect of the deformation on the separator.

In certain areas of the electrode, the gap may be larger or smaller than in other areas.

In a given region of the electrode, the gap may be constant along a direction parallel to the winding direction, or may increase gradually or in steps along a direction parallel to the winding direction.

The gap may be between 0.2 mm and 4 mm.

The segments have a geometric shape in which the width in the winding direction decreases from the bottom to the top, and the lower interior angle may increase gradually or in stages from the core side to the outer periphery side.

The multiple segments may include multiple segment groups in which adjacent segments in the winding direction have the same bottom interior angle. Managing the segments in groups makes design and manufacturing easier.

The lower interior angle θ of each of the segments belonging to a segment group can be the same as or larger than the lower interior angle of each of the segments belonging to a segment group arranged closer to the core. The curvature of a jelly-roll type electrode assembly decreases toward the outer periphery. Therefore, by making the lower interior angle larger for segments arranged closer to the outer periphery, the gap between adjacent segments in the circumferential direction of the electrode assembly can be minimized, which helps ensure the welding strength of the current collector, as described below.

The plurality of said segments may include a plurality of segment groups in which adjacent segments in the winding direction have the same first element selected from the lower interior angle θ, the axial height H of the segment, the winding direction width D of the segment, the shape of the segment, the height of the bottom of the cutting groove between the two segments, and the separation pitch P between the two segments.

Here, the first elements may be different between the sub-segment segments belonging to different sub-segment groups.

When the first element is a lower interior angle of a segment, the lower interior angle of each of the segments belonging to a segment group may be greater than the lower interior angle of each of the segments belonging to a segment group located closer to the core.

When the first element is the height of the segment in the axial direction (the winding axis of a jelly roll type), the height of each segment belonging to a segment group can be higher than the height of each segment belonging to a segment group arranged closer to the core. Then, when the segment arranged on the outer periphery side is folded, the number of segments overlapping with the segment arranged closer to the core can be further increased, and by maintaining a uniform number of overlaps of the folded segments in the radial direction of the electrode assembly, a folded surface area suitable for welding the current collector and easy to weld can be secured.

When the first element is the width of the segments in the winding direction, the width of each segment in a segment group in the winding direction can be wider than the width of each segment in a segment group arranged closer to the core. The electrode assembly wound into a jelly roll shape has a larger radius of curvature toward the outer periphery. Therefore, it is preferable that the width in the winding direction gradually increases so that the segments can be folded smoothly.

Segments belonging to the same segment group may have the same second element selected not only from the first element but also from the bottom interior angle of the segment, the axial height of the segment, the winding direction width of the segment, the shape of the segment, the height of the bottom of the cutting groove between the two segments, and the spacing pitch between the two segments so as not to overlap with the first element.

For example, the inner angle of the bottom of the segment, the axial height of the segment, the width of the segment in the winding direction, the shape of the segment, the height of the bottom of the cutting groove between two segments, and the separation pitch between two segments may all be approximately the same.

The second element may be different between the segments belonging to different segment groups. For example, the lower interior angle of the segment, the axial height of the segment, and the width of the segment in the winding direction may be different between the segments belonging to different segment groups.

Between the multiple minute segment groups, there may be an inter-group separation distance Db that is greater than the separation pitch between minute segments within the same minute segment group.

The group spacing Db can provide an electrolyte-impregnated portion that is not covered by the folded pieces on the surface perpendicular to the axial direction of the electrode assembly. The area corresponding to the electrolyte-impregnated portion is not welded to the current collector, which can improve electrolyte impregnation.

The segment groups separated by the inter-group spacing may be arranged radially with respect to the center of the electrode assembly to form a plurality of segment alignment portions. The electrolyte impregnation portion formed by the area where the inter-group spacing is wound may also be arranged radially with respect to the center of the electrode assembly. This makes it possible to ensure a welding area with the current collector while also ensuring a passage through which the electrolyte can be impregnated.

The segments included in the segment alignment section may be bent radially toward the core of the electrode assembly to form a bent surface area with a plurality of separation regions.

The circumferential angle between adjacent segment alignment parts (or folded surface regions) in the circumferential direction may be approximately 30°, 40°, 45°, 60°, 72°, 90°, 120°, or 180°. The angle is the angle between adjacent angle measurement lines in the circumferential direction when a line connecting the geometric center of each segment alignment part (or folded surface region) from the core center of the electrode assembly is defined as an angle measurement line. The geometric center is the geometric center of a figure approximately formed by the outer periphery of the segment alignment part (or folded surface region) when the segment alignment part (or folded surface region) is viewed from the axial direction. The geometric center may be the center of gravity of the figure.

The current collector may be welded to multiple folded surface areas. The welds may be 12, 9, 8, 6, 5, 4, 3, or 2 equally spaced circumferentially.

At least one of the spacing between the groups and the width of the segment groups in the winding direction may increase gradually or stepwise from the core toward the outer periphery. This allows the shape of the folded surface area formed by folding the segments and/or the axial surface of the electrode assembly not covered by the segments to be substantially fan-shaped with no central area.

The uncoated portion may include a first portion adjacent to the core of the electrode assembly, a second portion adjacent to the outer peripheral surface of the electrode assembly, and a third portion interposed between the first portion and the second portion.

The third portion may include the segment.

The second portion may not have a dividing structure.

Preferably, at least one of the first portion and the second portion may have a relatively lower height in the winding axis direction than the third portion.

The first and third parts may be directly connected without a section connecting them, or may be connected via a section connecting them.

The third part and the second part may be directly connected without a section connecting them, or may be connected via a section connecting them.

In the winding direction, the section of the first portion may start from the core side end.

In the winding direction, the length of the third portion may be longer than the lengths of the first portion and the second portion.

In the winding direction, the second portion may include at least the final turn that is exposed at the outermost edge of the electrode assembly.

The height of the plain part in a given section may mean the average height of that section or the maximum height in that section.

The height of the first portion may be constant along the winding direction. That is, the first portion may not have a segment.

In at least a portion of the third portion, the height of the segment may increase from the core side toward the outer periphery.

At this time, the height of the segments can increase in stages.

In addition, as the height increases stepwise, the length (width) in the winding direction of the section corresponding to each height may also increase stepwise.

The second portion may also include the segment.

The segments can be bent in the radial direction of the electrode assembly.

The segments can be bent toward the core, i.e., in a centripetal direction, toward the central axis of the electrode assembly.

The first portion may not have a split piece and may not be bent.

The final turn may not include the segment. Also, the height of the final turn may be lower than the third portion. When forming a jelly roll type electrode assembly, if the final turn has a segment that can be folded, handling of the electrode assembly becomes cumbersome because unexpected deformation of the segment must be prevented. By removing the segment of the final turn, such cumbersomeness can be reduced.

The electrode assembly has a hollow portion extending in the axial direction at its center, and the folded segment does not need to block the hollow portion in the direction toward the core.

The folded third portion may overlap in the axial direction.

The folded third portion and second portion may overlap in the axial direction.

Each of the multiple segments may be trapezoidal.

In one embodiment, the height of at least a portion of the third section in the axial direction of winding may increase stepwise from the core side toward the outer periphery.

In another embodiment, at least a portion of the third portion may be divided into a plurality of segments.

The uncoated portion may be divided by a cutting groove extending from the axial end of the winding shaft toward the axial center (from the axial end of the electrode assembly toward the axial center). The shape of the cutting groove is determined by the shape of the sides of the divided pieces located on both sides of the cutting groove. If the uncoated portion is simply cut without removing at least a portion of the uncoated portion at the notch through notching, the cutting line may also be considered as a cutting groove.

In yet another embodiment, each of the segments may have a rectangular, trapezoidal, triangular, parallelogram, semicircular, or semielliptical shape.

In one embodiment, each of the plurality of segments is a trapezoid, and the lower interior angle of the trapezoid may increase from the core side to the outer periphery side for each of the plurality of segments individually or in groups.

The segment allows the axial extension length of the plain portion to vary along the winding direction. For ease of explanation, if the axial extension length of the plain portion at a given position in the winding direction (the axial distance to the tip) is simply referred to as the height, it will be possible to clearly understand what is meant by the height of the plain portion at the first winding direction position being higher than the height of the plain portion at the second winding direction position.

In the embodiment, when describing the height of the plain area, the relative value of the height of the plain area measured at different positions in the winding direction is more meaningful than the absolute value of the height of the plain area, so the specification of the line (zero point) that serves as the reference point for measuring the height of the plain area will be omitted.

The height of the uncoated portion may differ between the portion corresponding to the top end of the segment, the portion corresponding to the cut groove provided to form the segment, and the portion corresponding to the bottom of the cut groove. That is, even if the shape and size of the segment and the shape and size of the cut groove are the same, the height of the uncoated portion measured in the axial direction may vary depending on the measurement position determined in the winding direction. For example, it is clear that, roughly speaking, the height of the uncoated portion at a winding direction position corresponding to the apex of the segment is higher than the height of the uncoated portion at a winding direction position corresponding to the bottom of the cut groove.

In addition, the height of the upper end of each segment may differ, the shape of each cut groove may differ, and the height of the bottom of the cut groove may also differ. In other words, since the shape and size of the segment and the shape and size of the cut groove may vary, the height of the plain portion measured in the axial direction may vary depending on the measurement position determined along the winding direction.

Meanwhile, the height of the segment may be defined as the axial distance (H) from the bottom of the cutting groove that defines the segment to the tip of the segment. If the heights of the bottoms of the cutting grooves on both sides of the segment are different, the height of the segment may be defined as the axial distance from the average height point of the bottom heights of the cutting grooves on both sides to the tip of the segment.

Preferably, at least one of the height in the winding axial direction and the width in the winding direction of the multiple segments can increase stepwise from the core side to the outer periphery side, either individually or for each group.

Preferably, each of the multiple segments satisfies at least one of the following conditions: a width of 1 mm to 11 mm in the winding direction, a height of 2 mm to 10 mm in the winding axial direction, and a separation pitch of 0.05 mm to 1 mm in the winding direction.

Preferably, there is a gap between the bottom of the cut groove of the segment and the active material layer, and the gap may be 0.2 mm to 4 mm.

Preferably, the multiple segments form multiple segment groups from the core side toward the outer periphery, and the segments belonging to the same segment group may have at least one of the same width in the winding direction, height in the winding axial direction, and spacing pitch in the winding direction.

Preferably, when the widths in the winding direction of three consecutive adjacent segment groups in the radial direction of the electrode assembly are W1, W2, and W3, respectively, the combination of segment groups may include a combination in which W3/W2 is smaller than W2/W1.

Preferably, the segments belonging to the same segment group may have at least one of the width in the winding direction, the height in the winding axial direction, and the separation pitch in the winding direction gradually increased from the core side to the outer periphery side.

In one embodiment, at least some of the multiple segment groups may be arranged on the same winding turn of the electrode assembly.

In other embodiments, the first portion or the second portion may not have a dividing structure of the plain portion.

The segments can be bent radially.

All of the multiple segments can be folded.

Some of the multiple segments do not need to be folded.

Preferably, the multiple segments can be folded toward the core and overlap each other along the winding axis.

Preferably, a cavity is provided in the core of the electrode assembly, and the cavity can be opened without being blocked by a plurality of segments bent toward the core.

Therefore, the radial length R of the first portion and the bending length H of the innermost segment of the third portion can satisfy the relation "H≦R".

In one embodiment, the height of the second portion may decrease stepwise or gradually from the core side to the outer periphery side.

In one embodiment, the second portion is divided into a plurality of segments, and the plurality of segments included in the second portion may have at least one of a width in the winding direction, a height in the winding axis direction, and a separation pitch in the winding direction that is greater than the plurality of segments included in the third portion.

If an imaginary straight line drawn along the winding direction (circumferential direction) so as to correspond to the height of the bottom of the cut groove is taken as the reference line DL, the reference line can be a straight line parallel to the winding direction (X-axis) of the plain portion.

The reference line can be positioned at a position corresponding to the bottom of a cutting groove provided between two adjacent pieces to form the piece.

The heights of the bottoms of the multiple cutting grooves may correspond to each other in the winding axis direction. In such a case, the position of the reference line may be defined at a position corresponding to the bottom of the cutting groove.

The bottom heights of the multiple cutting grooves may be different.

When most of the bottoms of the multiple cut grooves (e.g., 50% or more) are located at a specific height and only the height of the bottoms of some of the cut grooves differs from the specific height, the position of the reference line can be determined corresponding to the specific height. That is, in such a case, the reference line can be determined based on the height of the bottom of the cut groove that occupies the maximum length in the winding direction. For example, if about 2/3 of the total length occupied by the bottoms of the cut grooves in the winding direction is the first height and the height of the bottom of the cut groove that corresponds to the remaining 1/3 differs from the first height, the reference line can be defined at a position corresponding to the first height.

If the heights of the bottoms of the multiple cut grooves are not concentrated at a specific height (if the ratio of the plain section in which the cut grooves having the highest frequency height are formed is less than 50% of the total length of the electrode), the reference line may be set to be located at the average height of the bottoms of the multiple cut grooves. For example, when the height is measured based on the boundary point between the active material layer and the plain section, if the length of the plain section in which the bottoms of the cut grooves are 2 mm high is 30% of the total length of the electrode, the length of the plain section in which the bottoms of the cut grooves are 3 mm high is 30% of the total length of the electrode in the winding direction, and the length of the plain section in which the bottoms of the cut grooves are 4 mm high is 40% of the total length of the electrode in the winding direction, the reference line may be located at a height of 3.1 mm, which is 2 x 0.3 + 3 x 0.3 + 4 x 0.4.

The position of the end SL of the separation membrane in the width direction (Y axis) can be regulated in relation to the reference line DL.

Of the multiple segments, the segment with the lowest height is referred to as the minimum segment.

When determining the minimum height of the segment, segments that are not folded may be excluded. That is, the minimum segment may refer to the segment that has the minimum height among the folded segments included in the folded surface area. The folded surface area refers to the area of the end surface of the electrode assembly where the segments are folded radially and overlap in multiple layers along the winding axis direction.

The minimum segment can be determined from among the segments that can be folded.

If the height of the segment is less than 2 mm, there is a risk that the segment will not bend smoothly due to interference between the separation membrane and the segment.

Therefore, the minimum segment can be determined from among segments having a height of 2 mm or more.

If the height of the split piece is less than 3 mm, it may not be bent smoothly in the intended direction during the folding process, or it may be formed in an unintended direction.

Therefore, the minimum segment can be determined from among segments having a height of 3 mm or more.

If the height of the segments is less than 4 mm, there is a risk that the welding between the segments and/or between the current collector and the segments will be incomplete.

Therefore, the minimum segment can be determined from among segments having a height of 4 mm or more.

If the height of the divided pieces is 5 mm or more, it is possible to fold them reliably during the folding process, even taking into account manufacturing errors.

Therefore, the minimum segment can be determined from among segments having a height of 5 mm or more.

The widthwise end SL of the separator may be located outside the electrode assembly within 30% of the height Ha of the minimum segment based on the reference line DL, or may be located inside the electrode assembly within 30% of the height Ha of the minimum segment.

In other words, the position of the separation membrane's end in the width direction can be in the range of "DL ± 0.3Ha".

The widthwise end SL of the separator may be located within 1.5 mm from the reference line DL toward the outer side of the electrode assembly, or within 1.5 mm from the inner side of the electrode assembly.

In other words, the position of the end SL of the separation membrane in the width direction can be in the range of "DL ± 1.5 mm".

The widthwise end SL of the separator may be located within 1.2 mm from the reference line DL toward the outer side of the electrode assembly, or within 1.2 mm from the reference line DL toward the inner side of the electrode assembly.

In other words, the position of the end SL of the separation membrane in the width direction can be in the range of "DL ± 1.2 mm".

The widthwise end SL of the separator may be located within 0.9 mm from the reference line DL toward the outer side of the electrode assembly, or within 0.9 mm from the inner side of the electrode assembly.

In other words, the position of the end SL of the separation membrane in the width direction can be in the range of "DL ± 0.9 mm".

The widthwise end SL of the separator may be located within 0.6 mm from the reference line DL toward the outer side of the electrode assembly, or within 0.6 mm from the reference line DL toward the inner side of the electrode assembly.

In other words, the position of the end SL of the separation membrane in the width direction can be in the range of "DL ± 0.6 mm".

The position of the end SL of the separation membrane in the width direction can be within the range of "DL ± 0.3Ha" and "DL ± 1.5mm".

The position of the end SL of the separation membrane in the width direction can be within the range of "DL±0.3Ha" and "DL±1.2mm".

The position of the end SL of the separation membrane in the width direction can be within the range of "DL ± 0.3Ha" and "DL ± 0.9mm".

The position of the end SL of the separation membrane in the width direction may be within the range of "DL±0.3Ha" and "DL±0.6mm".

The separation membrane may include a porous polymer substrate and a porous coating layer located on the surface of the porous polymer substrate and including inorganic particles and a binder polymer.

The porous coating layer may be located on both sides of the porous polymer substrate.

The multiple segments may have a predetermined spacing pitch.

The separation pitch can be determined by the distance between the bottom corners of two adjacent segments.

The spacing may be 0.5 mm or more. If the spacing is less than 0.5 mm, stress may be concentrated, causing cracks at the bottom of the corresponding cut groove during processing, winding, bending, etc.

The lower corners of the two pieces may be connected in a straight line. That is, the bottom portion of the cutting groove may be a flat, straight line extending in the winding direction (X-axis).

A rounded reinforcement may be added to the bottom corner.

The radius r of the round reinforcement portion may be 0.02 mm or more. If the radius is 0.02 mm or more, the effect of dispersing stress can be reliably achieved.

The radius of the round reinforcement portion may be 0.1 mm or less. If the radius exceeds 0.1 mm, the stress dispersion effect will not increase any more, and the space near the bottom of the cut groove may decrease, hindering the impregnation of the electrolyte.

The spacing may be 1 mm or less. If the spacing exceeds 1 mm, impregnation will not increase, and gaps may occur between the folded pieces, causing the current collector to be insufficiently welded.

The separation pitch can be determined in relation to the width, measured in the winding direction, of the adjacent segments that define it.

For example, as the width of the segments in the winding direction increases, the spacing between the segments may also tend to increase. This can result in more uniform electrolyte impregnation.

The width of the segments in the winding direction may tend to gradually increase from the core side to the outer periphery side of the electrode assembly.

The width of the segment in the winding direction may increase gradually or in steps from the core side to the outer periphery side of the electrode assembly.

As a result, the spacing pitch can also increase gradually or stepwise from the core side to the outer periphery side of the electrode assembly.

In order to achieve the above object, a battery according to another aspect of the present invention includes an electrode assembly in which a core and an outer circumferential surface are defined by winding a first electrode, a second electrode, and a separator interposed between the first electrode and the second electrode around a winding shaft, a battery housing that houses the electrode assembly and is electrically connected to one of the first electrode and the second electrode and has a first polarity, a sealing body that seals an open end of the battery housing, and a terminal that is electrically connected to the other of the first electrode and the second electrode and has a second polarity with a surface exposed to the outside.

Preferably, at least one of the first electrode and the second electrode may include a plain portion at the long edge where the active material layer is not coated.

Preferably, at least a portion of the uncoated portion is used as an electrode tab by itself, and the uncoated portion includes a first portion adjacent to the core of the electrode assembly, a second portion adjacent to the outer peripheral surface of the electrode assembly, and a third portion interposed between the first portion and the second portion, and at least one of the first portion and the second portion may have a relatively lower height in the winding axis direction than the third portion.

In one embodiment, the second portion has a relatively lower height in the winding axial direction than the third portion, and the battery housing has a beading portion pressed inward at an end adjacent to the open end, and the inner peripheral surface of the beading portion facing the periphery of the upper end of the electrode assembly and the second portion may be spaced apart by a predetermined distance.

Preferably, the pressing depth D1 of the beading portion and the distance D2 from the inner peripheral surface of the battery housing to the boundary point between the second portion and the third portion satisfy the relational expression "D1≦D2".

In one embodiment, the battery according to one aspect of the present invention may further include a current collector electrically connected to the third portion, and an insulator covering the current collector and having a periphery interposed and fixed between the inner circumferential surface of the beading portion and the current collector.

In other embodiments, the diameter of the current collector and the outermost diameter of the third portion may be smaller than the minimum inner diameter of the inner circumferential surface of the beading portion, and the diameter of the current collector may be the same as or larger than the outermost diameter of the third portion.

In yet another embodiment, the current collector may be positioned higher than the beading portion.

Preferably, at least a portion of the third portion is bent from the outer periphery side toward the core side, and a cavity is provided in the core of the electrode assembly, and the cavity can be open to the outside without being blocked by the bent structure of the third portion.

Therefore, the third portion includes a plurality of segments cut along the winding direction of the electrode assembly, and the plurality of segments are bent from the outer periphery side toward the core side, and the radial length R of the first portion and the bent length H of the segment located at the innermost side of the third portion may satisfy the relational expression "H≦R".

Preferably, each of the plurality of segments may have a rectangular, trapezoidal, triangular, parallelogram, semicircular or semielliptical shape.

Preferably, each of the multiple segments satisfies at least one of the following conditions: a width of 1 mm to 11 mm in the winding direction, a height of 2 mm to 10 mm in the winding axial direction, and a separation pitch of 0.05 mm to 1 mm in the winding direction.

Preferably, there is a gap between the bottom of the cut groove of the segment and the active material layer, and the gap may be 0.2 mm to 4 mm.

Preferably, the plurality of segments form a plurality of groups, and the segments belonging to each group have at least one of the same width in the winding direction, height in the winding axial direction, and separation pitch in the winding direction, and at least one of the plurality of groups can constitute the same winding turn of the electrode assembly.

Preferably, when the widths in the winding direction of three consecutive adjacent segment groups in the radial direction of the electrode assembly are W1, W2, and W3, respectively, the combination of segment groups may include a combination in which W3/W2 is smaller than W2/W1.

In one embodiment, the sealing body includes a cap that seals the open end of the battery housing and a gasket that encloses the periphery of the cap and is crimped to the upper end of the battery housing, and the terminal having the second polarity may be the cap.

In another embodiment, the battery according to one aspect of the present invention may further include a current collector electrically connected to the uncoated portion of the second electrode having the first polarity and having at least a portion of its periphery joined to the side wall of the battery housing. In this case, the sealing body may include a cap with no polarity and a gasket that encloses the periphery of the cap and is crimped to the upper end of the battery housing, and the battery housing may include a rivet terminal that is insulatively attached to a through hole formed in the center of the closed surface, electrically connected to the first electrode, and has the second polarity.

The technical objective of the present invention is achieved by a battery pack including a plurality of the above-mentioned batteries.

Preferably, the battery has a height to diameter ratio of greater than 0.4.

Preferably, the battery form factor may be 46110, 4875, 48110, 4880 or 4680.

Preferably, the resistance of the battery may be 4 mΩ or less.

According to one embodiment, in the battery pack, the batteries are arranged in a predetermined number of rows, and the electrode terminals of each battery and the outer surface of the bottom of the battery housing can be arranged facing upward.

In another embodiment, the battery pack may include multiple bus bars connecting multiple batteries in series and parallel.

Preferably, the bus bars are disposed on the upper portions of the batteries, and each bus bar may include a body portion extending between the electrode terminals of adjacent batteries, a plurality of first bus bar terminals extending to one side of the body portion and electrically connecting to the electrode terminals of the battery located on that side, and a plurality of second bus bar terminals extending to the other side of the body portion and electrically connecting to the outer surface of the bottom of the battery housing of the battery located on that other side.

The technical object of the present invention is also achieved by a vehicle including the above-mentioned battery pack.

According to one aspect of the present invention, the uncoated portions protruding from the upper and lower sides of the electrode assembly themselves can be used as electrode tabs, thereby reducing the internal resistance of the battery and increasing the energy density.

In addition, according to one aspect of the present invention, by improving the structure of the uncoated portion of the electrode assembly, the electrode assembly does not interfere with the inner surface of the battery housing during the process of forming the beading portion of the battery housing, and internal short circuits in the cylindrical battery caused by partial deformation of the electrode assembly can be prevented.

In addition, according to one aspect of the present invention, by improving the structure of the uncoated portion of the electrode assembly, it is possible to prevent the uncoated portion from tearing when it is bent, and to sufficiently increase the number of overlapping layers of the uncoated portion, thereby improving the welding strength of the current collector.

In addition, according to one aspect of the present invention, by applying a segment structure to the uncoated portion of the electrode and optimizing the dimensions of the segments (width, height, and spacing pitch) to sufficiently increase the number of segments stacked in the area used as the welding target area, the physical properties of the area where the current collector is welded can be improved.

In addition, according to one aspect of the present invention, by applying a structure in which a current collector is welded over a wide area to the folded surface area formed by bending the divided pieces, it is possible to provide an electrode assembly with improved energy density and reduced resistance.

In addition, according to one aspect of the present invention, a cylindrical battery can be provided with an improved design that allows electrical wiring to be performed at the top.

In addition, according to one aspect of the present invention, by improving the structure of the uncoated portion adjacent to the core of the electrode assembly, it is possible to prevent the cavity in the core of the electrode assembly from being blocked when the uncoated portion is bent, and to facilitate the electrolyte injection process and the welding process between the battery housing (or terminal) and the current collector.

In addition, according to one aspect of the present invention, the folded surface area formed by folding the uncoated portion is provided in a position corresponding to the welding portion with the current collector, so that the welding of the current collector can be performed stably and the impregnation of the electrolyte can be ensured.

In addition, according to one aspect of the present invention, electrolyte impregnation can be sufficiently ensured even if the uncoated portion of the electrode assembly is folded.

In addition, according to one aspect of the present invention, it is possible to provide a cylindrical battery having a structure in which the internal resistance is low, internal short circuits are prevented, and the welding strength between the current collector and the uncoated portion is improved, as well as a battery pack and an automobile including the cylindrical battery.

In particular, the present invention provides a cylindrical battery having a height-to-diameter ratio of 0.4 or more and a resistance of 4 mΩ or less, and a battery pack and a vehicle including the cylindrical battery.

The present invention also provides a variety of other effects, which will be described later with reference to embodiments. However, explanations of effects that can be easily inferred by ordinary engineers will be omitted.

The following drawings attached to this specification are intended to illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to provide a better understanding of the technical concepts of the present invention. Therefore, the present invention should not be interpreted as being limited to only the matters depicted in the drawings.

FIG. 1 is a plan view showing the structure of an electrode used in the manufacture of a conventional tabless cylindrical battery. FIG. 1 is a diagram showing an electrode winding process for a conventional tabless cylindrical battery. 1 is a diagram showing a process in which a current collector is welded to a folded surface area of a non-coating portion in a conventional tabless cylindrical battery. FIG. 2 is a plan view showing the structure of an electrode according to the first embodiment of the present invention. FIG. 6 is a plan view showing a structure of an electrode according to a second embodiment of the present invention. FIG. 11 is a plan view showing a structure of an electrode according to a third embodiment of the present invention. FIG. 13 is a plan view showing the structure of an electrode according to a fourth embodiment of the present invention. FIG. 2 is a diagram illustrating the definition of the width, height, and spacing pitch of segments according to an embodiment of the present invention. 1 is a diagram illustrating a circular arc formed by the lower end of a segment, the width of which is defined when the electrode is wound according to an embodiment of the present invention, based on the center of a core of an electrode assembly. 1 is a diagram showing a relationship between segment heights _h1 , _h2 , _h3 , and _h4 , core radius _rc , and winding turn radii _r1 , _r2 , _r3 , and _r4 at which segment segments begin to appear according to an embodiment of the present invention; 13 is a conceptual diagram for determining the maximum value h _max of the height H of a segment in a segment height variable section. FIG. FIG. 13 is a schematic diagram for explaining a formula for determining a lower interior angle θ of a segment. FIG. 13 is a plan view showing a modified structure of an electrode according to a fourth embodiment of the present invention. This is a top view showing an example in which, when an electrode according to a modified embodiment of the present invention is wound up as an electrode assembly, a plurality of segment alignment portions (folded surface areas) and a plurality of electrolyte-impregnated portions are formed radially on one side end surface of the electrode assembly. This is a top view showing an example in which, when an electrode according to a modified embodiment of the present invention is wound up as an electrode assembly, a plurality of segment alignment portions (folded surface areas) and a plurality of electrolyte-impregnated portions are formed radially on one side end surface of the electrode assembly. 13 is a diagram showing a structure in which a segment group included in a segment alignment portion formed in a sector shape is arranged in different winding turns according to an embodiment of the present invention. FIG. FIG. 13 is a plan view showing the structure of an electrode according to a fifth embodiment of the present invention. 13 is a diagram illustrating the definition of the width, height, and spacing pitch of segments according to another embodiment of the present invention. FIG. 13 is a plan view showing a modified structure of an electrode according to a fifth embodiment of the present invention. 13A to 13C are diagrams showing segmented structures according to various modified embodiments of the present invention; 4 is a schematic diagram showing a cross section of a bent surface region formed when a segment is bent toward a core of an electrode assembly; FIG. FIG. 2 is a top perspective view illustrating an electrode assembly having a folded surface region formed thereon; 13 is a graph showing the results of counting the number of stacked pieces along a radial direction in a folded surface region of a positive electrode formed on an upper portion of an electrode assembly according to Examples 1-1 to 1-7 and a comparative example. 13 is a graph showing the results of counting the number of stacked pieces measured along the radial direction in a folded surface region of a positive electrode formed on an upper portion of an electrode assembly according to Examples 2-1 to 2-5, 3-1 to 3-4, 4-1 to 4-3, 5-1, and 5-2. 13 is a graph showing the results of counting the number of stacked pieces measured along a radial direction in a folded surface region of a positive electrode formed on an upper portion of an electrode assembly according to Examples 6-1 to 6-6 and Examples 7-1 to 7-6. 2 is a top view of an electrode assembly showing a uniform lamination number section b1 and a reduced lamination number section b2 in a folded surface region of a segment according to an embodiment of the present invention. FIG. 1 is a cross-sectional view of a jelly roll-type electrode assembly in which the electrodes of the first embodiment are applied to a first electrode (positive electrode) and a second electrode (negative electrode) taken along the Y-axis direction (winding axis direction). FIG. FIG. 11 is a cross-sectional view taken along the Y-axis direction (winding axis direction) of a jelly roll-type electrode assembly in which the electrodes of the second embodiment are applied to a first electrode (positive electrode) and a second electrode (negative electrode). FIG. 11 is a cross-sectional view of a jelly roll-type electrode assembly in which any one of the electrodes of the third to fifth embodiments (variations thereof) is applied to a first electrode (positive electrode) and a second electrode (negative electrode) along the Y-axis direction (winding axis direction). 11 is a cross-sectional view of an electrode assembly according to still another embodiment of the present invention, taken along the Y-axis (winding axis) direction. 11 is a cross-sectional view of an electrode assembly according to still another embodiment of the present invention, taken along the Y-axis (winding axis) direction. 11 is a cross-sectional view of an electrode assembly according to still another embodiment of the present invention, taken along the Y-axis (winding axis) direction. 2 is a cross-sectional view of a cylindrical battery according to an embodiment of the present invention taken along the Y-axis direction. 4 is a cross-sectional view of a cylindrical battery according to another embodiment of the present invention taken along the Y-axis direction. 11 is a cross-sectional view of a cylindrical battery according to yet another embodiment of the present invention, taken along the Y-axis direction. 11 is a cross-sectional view of a cylindrical battery according to yet another embodiment of the present invention, taken along the Y-axis direction. 11 is a cross-sectional view of a cylindrical battery according to yet another embodiment of the present invention, taken along the Y-axis direction. 11 is a cross-sectional view of a cylindrical battery according to yet another embodiment of the present invention, taken along the Y-axis direction. 11 is a cross-sectional view of a cylindrical battery according to yet another embodiment of the present invention, taken along the Y-axis direction. 11 is a cross-sectional view of a cylindrical battery according to yet another embodiment of the present invention, taken along the Y-axis direction. 11 is a cross-sectional view of a cylindrical battery according to yet another embodiment of the present invention, taken along the Y-axis direction. FIG. 2 is a top view showing a structure of a first current collector according to an embodiment of the present invention. FIG. 4 is a top view showing a structure of a second current collector according to an embodiment of the present invention. FIG. 1 is a top view showing a state in which a plurality of cylindrical batteries are electrically connected to each other. FIG. 29 is a partially enlarged view of FIG. 28 . 1 is a diagram illustrating a schematic configuration of a battery pack according to an embodiment of the present invention; 1 is a schematic diagram of a vehicle including a battery pack according to an embodiment of the present invention;

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. Prior to this, the terms and words used in this specification and claims are not to be interpreted as being limited to their ordinary and dictionary meanings, but are to be interpreted as having meanings and concepts corresponding to the technical ideas of the present invention, in accordance with the principle that the inventor himself can appropriately define the concepts of terms in order to best describe the invention.

Therefore, it should be understood that the embodiment described in this specification and the configuration shown in the drawings are merely the most preferred embodiment of the present invention and do not represent the entire technical idea of the present invention, and that there may be various equivalents and modifications that can be substituted for them at the time of this application.

In addition, to aid in understanding the invention, the accompanying drawings may not be drawn to scale, and the dimensions of some components may be exaggerated. Also, the same reference numbers may be used for the same components in different embodiments.

The expression that two objects to be compared are identical means that they are "substantially identical." Therefore, "substantially identical" may include cases where there is a deviation that is considered to be a low level in the industry, for example, a deviation of 5% or less. In addition, the expression that a certain parameter is uniform in a given region means that it is uniform from an average perspective in that region.

In addition, although terms such as "first" and "second" are used to indicate various components, these terms are not intended to limit the components. These terms are merely used to distinguish one component from another, and unless otherwise specified, the first component can also be the second component.

Throughout the specification, each element may be singular or plural unless otherwise stated.

When an arbitrary configuration is disposed "on (or under)" a component or "above (or below)" a component, this does not only mean that the arbitrary configuration is disposed in contact with the upper surface (or lower surface) of the component, but also that other configurations may be interposed between the component and the arbitrary configuration disposed above (or below) the component.

In addition, when a certain component is "coupled," "coupled," or "connected" to another component, this does not only mean that the components are directly coupled or connected to each other, but also that other components are "interposed" between each component, or that each component is "coupled," "coupled," or "connected" through other components.

In addition, singular expressions used in this specification include plural expressions unless the context clearly indicates otherwise. In this application, terms such as "comprise" or "include" are not necessarily interpreted as including all of the components or steps described in the specification, and may not include some of the components or steps, and may further include additional components or steps.

Throughout the specification, "A and/or B" means A, B, or A and B, unless otherwise specified, and "C-D" means C or more and D or less, unless otherwise specified.

For ease of explanation, in this specification, the direction along the length of the winding shaft of the electrode assembly wound into a jelly roll is referred to as the axial direction (Y-axis). The direction surrounding the winding shaft is referred to as the circumferential direction or outer circumferential direction (X-axis). The directions approaching or moving away from the winding shaft are referred to as the radial direction or radial direction. Of these, the direction approaching the winding shaft is referred to as the centripetal direction, and the direction moving away from the winding shaft is referred to as the centrifugal direction.

First, an electrode assembly according to one embodiment of the present invention will be described. The electrode assembly may be a jelly-roll type electrode assembly having a structure in which a sheet-like first electrode, a second electrode, and a separator interposed between the first electrode and the second electrode are wound in one direction. However, the present invention is not limited by the type of electrode assembly.

Preferably, at least one of the first electrode and the second electrode includes an uncoated portion on the long side end in the winding direction where the active material is not coated. At least a portion of the uncoated portion is used as an electrode tab itself. The uncoated portion includes a core-side uncoated portion adjacent to the core of the electrode assembly, an outer-periphery-side uncoated portion adjacent to the outer peripheral surface of the electrode assembly, and an intermediate uncoated portion interposed between the core-side uncoated portion and the outer-periphery-side uncoated portion.

Preferably, at least one of the core side plain portion and the outer periphery side plain portion is relatively lower in height than the intermediate plain portion.

Figure 4 is a plan view showing the structure of electrode 40 according to the first embodiment of the present invention.

Referring to FIG. 4, the electrode 40 of the first embodiment includes a current collector 41 made of a metal foil, and an active material layer 42. The metal foil may be a conductive metal, such as aluminum or copper, and is appropriately selected according to the polarity of the electrode 40. An active material layer 42 is formed on at least one surface of the current collector 41. The active material layer 42 is formed along the winding direction (X-axis). The electrode 40 includes a plain portion 43 at the end of the long side in the winding direction (X-axis). The plain portion 43 is a portion of the current collector 41 that is not coated with an active material. The region of the current collector 41 on which the active material layer 42 is formed may be referred to as an active material portion.

In the electrode 40, the width of the active material portion in the direction of the short side of the current collector 41 may be 50 mm to 120 mm, and the length of the active material portion in the direction of the long side of the current collector 41 may be 3 m to 5 m. Therefore, the ratio of the short side to the long side of the active material portion may be 1.0% to 4.0%.

Preferably, in the electrode 40, the width of the active material portion in the direction of the short side of the current collector 41 may be 60 mm to 70 mm, and the length of the active material portion in the direction of the long side of the current collector 41 may be 3 m to 5 m. Therefore, the ratio of the short side to the long side of the active material portion may be 1.2% to 2.3%.

The ratio of the short side to the long side of the active material portion is significantly smaller than the 6% to 11% ratio of the long side to the short side of the active material portion of electrodes used in cylindrical batteries with 1865 or 2170 form factors.

Preferably, the current collector 41 has an elongation rate of 1.5% to 3.0% and a tensile strength of 25 gf/mm ² to 35 kgf/mm ^2. The elongation rate and tensile strength can be measured according to the measurement method of IPC-TM-650. The electrode 40 is manufactured by forming an active material layer 42 on the current collector 41 and then compressing the same. During compression, the non-coated portion 43 region and the active material layer 42 region have different elongation rates. Therefore, the electrode 40 after compression swells, and the longer the electrode 40 is, the more severe the swell becomes.

Optimization of the elongation rate and tensile strength of the current collector 41 reduces the camber length after crimping to less than 20 mm when the length of the electrode 40 is at the 4 m level. The camber length is the maximum amount of deflection of the electrode 40 in the winding direction (X-axis) when the electrode 40 with undulations is unfolded. The maximum amount of deflection can be measured at the outer end. An electrode 40 with an optimized elongation rate and tensile strength of the current collector 41 has a short camber length, so no meandering defects occur during the notching operation of the plain portion 43 or the winding process of the electrode 40.

The smaller the elongation ratio of the current collector 41, the more likely it is to break. If the elongation ratio of the current collector 41 is less than 1.5%, the rolling processability of the current collector 41 is reduced, and when the electrode 40 coated with the active material layer 42 is pressure-bonded to the current collector 41, the current collector 41 may break. On the other hand, if the elongation ratio of the current collector 41 exceeds 3.0%, the active material portion of the electrode 40 is excessively stretched, and the camber length increases significantly. If the tensile strength of the current collector 41 is less than 25 kgf/ ^mm2 or exceeds 35 kgf/ ^mm2 , the electrode processability of the electrode 40 is reduced.

The camber phenomenon is particularly problematic in positive electrode current collectors made of aluminum foil. According to the present invention, the camber phenomenon can be suppressed by using an aluminum foil with an elongation ratio of 1.5% to 3.0% and a tensile strength of 25 kgf/mm ² to 35 kgf/mm ² as a current collector. It is preferable to form an active material layer on such a current collector and use it as a positive electrode.

Preferably, an insulating coating layer 44 may be formed at the boundary between the active material layer 42 and the uncoated portion 43. Hereinafter, for convenience of explanation, the insulating coating layer 44 may be simply referred to as an insulating layer 44. The insulating coating layer 44 is formed to overlap at least a portion of the boundary between the active material layer 42 and the uncoated portion 43. The insulating coating layer 44 prevents a short circuit between two electrodes of opposite polarity facing each other via a separator. The insulating coating layer 44 may cover the boundary between the active material layer 42 and the uncoated portion 43 with a width of 0.3 mm to 5 mm. The width of the insulating coating layer 44 may vary along the winding direction of the electrode 40. The insulating coating layer 44 includes a polymer resin and may include an inorganic filler such as Al ₂ O _3. The portion of the current collector 41 covered by the insulating coating layer 44 may be considered as an uncoated portion since it is not a region coated with an active material layer.

The uncoated portion 43 includes a core-side uncoated portion B1 adjacent to the core side of the electrode assembly, an outer-periphery-side uncoated portion B3 adjacent to the outer-periphery-side of the electrode assembly, and an intermediate uncoated portion B2 interposed between the core-side uncoated portion B1 and the outer-periphery-side uncoated portion B3.

When the electrode 40 is wound into a jelly roll-type electrode assembly, the core-side plain area B1, the outer periphery-side plain area B3, and the middle plain area B2 can be defined as the plain area adjacent to the core side, the plain area adjacent to the outer periphery, and the plain area excluding these, respectively.

Hereinafter, the core side uncoated portion B1, the outer periphery side uncoated portion B3, and the middle uncoated portion B2 will be referred to as the first portion, the second portion, and the third portion, respectively.

As an example, the first portion B1 may be an uncoated portion of the electrode region including the innermost winding turn, and the second portion may be an uncoated portion of the electrode region including the outermost winding turn. The winding turns may be counted relative to the core end of the electrode assembly.

As another example, the boundary between B1 and B2 may be appropriately defined as a point where the height (or change pattern) of the uncoated portion changes substantially from the core side to the outer periphery side of the electrode assembly, or as a point that is a certain percentage based on the radius of the electrode assembly (e.g., 5%, 10%, 15% of the radius, etc.).

The B2/B3 boundary may be defined as a point where the height (or change pattern) of the uncoated portion changes substantially from the outer periphery side to the core side of the electrode assembly, or as a certain percentage point based on the radius of the electrode assembly (e.g., 85%, 90%, 95% of the radius, etc.). Once the B1/B2 boundary and the B2/B3 boundary are identified, the third portion B2 may be automatically identified.

If only the B1/B2 boundary is specified, the B2/B3 boundary can be appropriately selected at a point near the outer periphery of the electrode assembly. As an example, the second portion can be defined as the uncoated portion of the electrode region that constitutes the outermost winding turn. On the other hand, if only the B2/B3 boundary is specified, the B1/B2 boundary can be appropriately selected at a point near the core side of the electrode assembly. As an example, the first portion can be defined as the uncoated portion of the electrode region that constitutes the innermost winding turn.

It is not excluded that another structure is interposed between the first part B1 and the third part B2. It is also not excluded that another structure is interposed between the third part B2 and the second part B3.

In the first embodiment, the height of the plain portion 43 is not constant, but varies relatively in the winding direction (X-axis). That is, the height of the second portion B3 (length in the Y-axis direction) is greater than or equal to 0, and is relatively lower than the first portion B1 and the third portion B2. Here, the height of each portion may be an average height or a maximum height, and so forth. In the winding direction, the length of the third portion B2 is even longer than the first portion B1 and the second portion B3.

Figure 5 is a plan view showing the structure of electrode 45 according to the second embodiment of the present invention.

Referring to FIG. 5, the electrode 45 of the second embodiment differs from the first embodiment only in that the height of the second portion B3 gradually decreases toward the outer periphery, and the other configurations are substantially the same.

In one variant, the second portion B3 can be deformed in a staircase shape (see dotted line) with a stepwise decrease in height.

Figure 6 is a plan view showing the structure of electrode 50 according to the third embodiment of the present invention.

Referring to FIG. 6, in the third embodiment of the electrode 50, the heights of the first portion B1 and the second portion B3 are equal to or greater than 0 and are relatively lower than the third portion B2. In addition, the heights of the first portion B1 and the second portion B3 may be the same or different.

Preferably, the height of the third portion B2 may be stepped, increasing in steps from the core side toward the outer periphery.

Patterns 1 to 7 are obtained by dividing the third portion B2 around the position where the height of the uncoated portion 43 changes. Preferably, the number of patterns and the height (length in the Y-axis direction) and width (length in the X-axis direction) of each pattern can be adjusted to maximize stress distribution during the bending process of the uncoated portion 43. The purpose of distributing the stress is to prevent the uncoated portion 43 from breaking when it is bent toward the core of the electrode assembly.

The width _dB1 of the first portion B1 is designed under the condition that the core of the electrode assembly is not blocked when the pattern of the third portion B2 is bent toward the core. The core refers to a cavity present at the winding center of the electrode assembly.

For example, the width d _B1 of the first portion B1 may increase in proportion to the bending length of the pattern 1. The bending length corresponds to the height of the pattern based on the bending point of the pattern.

Preferably, the width _dB1 of the first portion B1 may be set such that the radial width of the winding turn formed by the first portion B1 is equal to or greater than the bend length of the pattern 1. In a variant, the width _dB1 of the first portion B1 may be set such that the value obtained by subtracting the radial width of the winding turn formed by the first portion B1 from the bend length of the pattern 1 is less than 0 or less than 10% of the core radius.

In a specific example, when the electrode 50 is used to manufacture an electrode assembly for a cylindrical battery with a form factor of 4680, the width d _B1 of the first portion B1 may be set to 180 mm to 350 mm depending on the diameter of the core of the electrode assembly and the folding length of the pattern 1.

In one example, the width of each pattern can be designed to form one or more winding turns of the electrode assembly.

In another example, the height of the third portion B2 may be stepped, increasing and then decreasing from the core side toward the outer periphery side.

In yet another example, the second part B3 can be modified to have the same structure as the second embodiment.

In yet another example, the pattern structure applied to the third portion B2 can be extended to the second portion B3 (see dotted line).

The third portion B2 can be bent in the radial direction of the electrode assembly based on an imaginary line connecting the tip of the first portion B1 and the tip of the second portion B3 in the winding direction.

Figure 7a is a plan view showing the structure of an electrode 60 according to a fourth embodiment of the present invention.

Referring to FIG. 7a, in the fourth embodiment of the electrode 60, the heights of the first part B1 and the second part B3 in the winding axis (Y-axis) direction are equal to or greater than 0 and are relatively lower than the third part B2. In addition, the heights of the first part B1 and the second part B3 in the winding axis (Y-axis) direction may be the same or different.

Preferably, the third portion B2 may include a plurality of segment pieces 61 in at least a portion of the section. The plurality of segment pieces 61 may have a height that increases stepwise from the core side toward the outer periphery side. The plurality of segment pieces 61 may have a geometric shape that decreases in width from the bottom toward the top. Preferably, the geometric shape is a trapezoid. The corners, i.e., the apex portions, of the trapezoid may be rounded or chamfered like a chamfer, rather than having sharp ends. As will be described later, the shape of the geometric shape may be modified in various ways.

The segment 61 may be formed by laser notching. The segment 61 may be formed by a known metal foil cutting process such as ultrasonic cutting or punching.

The third portion B2 may be bent in the radial direction of the electrode assembly based on an imaginary line connecting the tip of the first portion B1 and the tip of the second portion B3 in the winding direction. In this case, the divided piece 61 may be bent based on the bottom of the cutting groove. The height of the bottom of the cutting groove between the divided pieces may correspond to the height of the first portion B1 and/or the height of the second portion B3.

In the fourth embodiment, in order to prevent damage to the active material layer 42 and/or the insulating coating layer 44 during the bending process of the plain portion 43, it is preferable to provide a certain gap between the bottom of the cut groove between the divided pieces 61 (G in FIG. 7b) and the active material layer 42. This is because when the plain portion 43 is bent, stress is concentrated near the bottom of the cut groove 63.

The gap can vary along the winding direction of the electrode 60. The gap is between 0.2 mm and 4 mm, preferably between 1.5 mm and 2.5 mm.

When the electrode 60 is a negative electrode, it is more preferable that the gap is 1.0 mm or more, and when the electrode 60 is a positive electrode, it is more preferable that the gap is 2.0 mm or more.

By adjusting the gap to the above numerical range, it is possible to prevent the active material layer 42 and/or the insulating coating layer 44 near the bottom of the cut groove 63 from being damaged by stress generated during the bending process of the plain portion 43.

Preferably, when the electrode 40 is wound into an electrode assembly, at least a portion of the insulating coating layer 44 may be exposed to the outside of the separator. In this case, when the segment 61 is folded, the insulating coating layer 44 may support the folding point.

The gap can prevent damage to the active material layer 42 and/or the insulating coating layer 44 due to tolerances when notching or cutting the segments 61. In one direction parallel to the winding direction, the gap can be substantially the same or can vary. In the latter case, the multiple segments can have varying gaps individually, in groups, or in two or more groups along one direction parallel to the winding direction.

The lower end of the divided piece 61 formed by the cut groove 63 may be a portion where bending is induced in the folding process of the divided piece 61. That is, in the folding process, the folding resistance is almost constant from the bottom end of the plain portion 43 to near the bottom of the cut groove 63, decreases sharply near the bottom of the cut groove 63, and then remains almost constant until it reaches the upper end of the divided piece 61.

The bottom of the cutting groove 63 and the insulating coating layer 44 may be spaced apart by 0.2 mm to 2.0 mm. If the distance is less than 0.2 mm, the above-mentioned damage prevention effect cannot be fully exerted, and if the distance is more than 2.0 mm, the damage prevention effect does not increase and the bending support effect of the insulating coating layer 44 may be reduced.

In one direction parallel to the winding direction, the separation distance between the bottom of the cut groove 63 and the insulating coating layer 44 may be substantially the same or may vary. In the latter case, the separation distance of the multiple segments may vary individually, in groups, or in two or more groups along one direction parallel to the winding direction.

When the electrode 60 is wound, the end of the insulating coating layer 44 in the winding axis (Y-axis) direction may be located in the range of -2 mm to 2 mm along the winding axis direction based on the end of the separator. The insulating coating layer 44 can prevent short-circuiting between two electrodes of opposite polarity facing each other through the separator and support the bending point when the divided piece 61 is bent. In order to improve the short-circuit prevention effect between the two electrodes, the insulating coating layer 44 may be exposed to the outside of the separator. In addition, in order to further maximize the short-circuit prevention effect between the two electrodes, the width of the insulating coating layer 44 may be increased so that the end of the insulating coating layer 44 in the winding axis (Y-axis) direction is located above the bottom of the cutting groove 63. In one example, the end of the insulating coating layer 44 in the winding axis direction may be located in the range of -2 mm to +2 mm based on the bottom of the cutting groove 63. The thickness of the insulating coating layer 44 may be thinner than the thickness of the active material layer 42. As a result, when the electrode 60 is laminated with the separation membrane, the insulating coating layer 44 and the separation membrane may be in weak contact with each other compared to the degree of adhesion between the active material layer 42 of the electrode 60 and the separation membrane, or a gap may be formed between the insulating coating layer 44 and the separation membrane.

The insulating coating layer 44 provides a supporting force to prevent the base end of the uncoated portion from being deformed during the bending process of the divided piece 61. However, even if the supporting force is weaker than the bending force and some deformation occurs, the deformation of the insulating coating layer 44 does not immediately and directly affect the separation membrane because there is a small gap between the insulating coating layer 44 and the separation membrane.

The multiple segments 61 may form multiple segment groups from the core side toward the outer periphery. The segment groups may be the same in at least one element among the lower interior angle between adjacent segments in the winding direction, the axial height of the segment, the winding width of the segment, the shape of the segment, the height of the bottom of the cutting groove between two segments, and the separation pitch between two segments.

Figure 7a shows an embodiment in which the width, height and spacing pitch of segments belonging to the same segment group are approximately the same.

Sub-segments belonging to different sub-segment groups may differ in at least one of the elements that are identical within the same group.

In other embodiments, the segments may be spaced apart in groups or in groups of two or more, with the spacing increasing gradually or stepwise from the core side to the outer periphery side, or vice versa.

In yet another embodiment, the spacing of the segments may be such that the spacing pitch increases gradually or stepwise from the core side to the outer periphery side and then decreases gradually or stepwise, or vice versa, in groups or in groups of two or more groups.

In yet another embodiment, the multiple segments may have a gap between the bottom of the cut groove 63 and the insulating coating layer 44 or active material layer 42 that increases gradually or stepwise from the core side to the outer periphery side, or vice versa.

In yet another embodiment, the gap between the bottom of the cut groove 63 and the insulating coating layer 44 or the active material layer 42 of the multiple segments may increase or decrease gradually or stepwise from the core side to the outer periphery side. Or vice versa.

In the embodiment of FIG. 7a, each segment group has different segment heights. In the electrode assembly, the separator SP may face the active material layer 42 and/or the insulating coating layer 44 of the electrode 60. Preferably, the end position of the separator SP may be adjusted to improve electrolyte impregnation.

In the electrode assembly, a line extending parallel to the winding direction (X-axis) based on the lowest point of the first part B1, the second part B3, and the third part B2 is defined as a reference line DL, and the part having the smallest height among the plurality of parts is defined as a minimum part. The end SL in the width direction of the separator SP may be located in the outer direction of the electrode assembly within 30% of the height Ha of the minimum part based on the reference line DL. Here, the outer direction of the electrode assembly means the direction from the active material layer 42 of the electrode 60 toward the uncoated portion 43.

Alternatively, the widthwise end SL of the separator SP may be located toward the inside of the electrode assembly within 30% of the height Ha of the minimum segment based on the reference line DL. Here, the inside of the electrode assembly means the direction from the uncoated portion 43 of the electrode 60 toward the active material layer.

Preferably, the height Ha of the minimum segment may correspond to the minimum value of the heights of the segments bent in the radial direction of the electrode assembly.

The reference line DL, which is a line extending parallel to the winding direction (X-axis) from the lowest point of the first part B1, the second part B3, and the third part B2, corresponds to the bottom of the cutting groove 63 between adjacent pieces, and the bottom of the cutting groove can be called a notching valley.

According to one embodiment of the present invention, by controlling the widthwise end of the separator SP to be located close to the reference line DL, the electrolyte flows into the electrode assembly along the notch valley (open space), increasing the impregnation speed. Specifically, when the electrolyte is injected into the battery housing in which the electrode assembly is inserted, the electrolyte moves to the notch valley between the segments of the uncoated portion of the electrode. The electrolyte is then impregnated into the notch valley between the segments, i.e., the end of the separator located close to the reference line, and finally into the active material layer of the electrode. As a result, the uniformity of electrolyte impregnation within the electrode assembly is increased.

The closer the widthwise end SL of the separator SP is located toward the outside of the electrode assembly, the more negatively it affects the welding characteristics. Conversely, the closer the widthwise end SL of the separator SP is located toward the inside of the electrode assembly, the greater the risk of a short circuit between the positive and negative electrodes.

Therefore, in one embodiment of the present invention, the widthwise end SL of the separation membrane SP is controlled to be located toward the outside of the electrode assembly within 30% of the height of the minimum segment based on the reference line DL, or to be located toward the inside of the electrode assembly within 30% of the height of the minimum segment.

According to one embodiment of the present invention, the widthwise end SL of the separator SP may be located within 1.5 mm from the reference line DL toward the outer side of the electrode assembly, or may be located within 1.5 mm from the reference line DL toward the inner side of the electrode assembly.

Figure 7b shows the definition of the width D, height H, and spacing pitch P of the trapezoidal segment 61.

Referring to FIG. 7b, the width D, height H and spacing P of the divided pieces 61 are designed to prevent the uncoated portion 43 from breaking near the bending point during bending and to ensure sufficient welding strength by sufficiently increasing the number of overlapping layers of the uncoated portion 43 while preventing abnormal deformation of the uncoated portion 43.

The bending of the segment 61 is performed at or above line G passing through the bottom of the cutting groove 63. The cutting groove 63 allows smooth and easy bending of the segment 61 in the radial direction of the electrode assembly.

The width D of the segment 61 is defined as the length between two points where two straight lines extending from the side edges 63b on both sides of the segment 61 intersect with a straight line extending from the bottom 63a of the cutting groove 63. The height H of the segment 61 is defined as the shortest distance between the top edge of the segment 61 and a straight line extending from the bottom 63a of the cutting groove 63. The separation pitch P of the segment 61 is defined as the length between two points where a straight line extending from the bottom 63a of the cutting groove 63 intersects with a straight line extending from the two side edges 63b connected to the bottom 63a. When the side edges 63b and/or the bottom edge 63a are curved, the straight lines may be replaced with tangent lines extending from the intersections of the side edges 63b and the bottom edge 63a to the side edges 63b and/or the bottom edge 63a.

Preferably, the width D of the divided pieces 61 is 1 mm or more. If D is less than 1 mm, when the divided pieces 61 are bent toward the core, the divided pieces 61 may not overlap to an extent that sufficient welding strength is ensured, or an empty space (gap) may be generated.

Preferably, the width D of the segment 61 can be adaptively adjusted according to the radius of the winding turn in which the segment 61 is located so that the segment 61 easily overlaps in the radial direction when the segment 61 is bent toward the core side of the electrode assembly.

FIG. 7c is a diagram showing an arc _A1A2 formed by the lower end of the segment 61 (line segment D _ab in FIG. 7b ), which defines the width D of the segment 61 when the electrode 60 is wound up according to an embodiment of the _{present invention} , with reference to the center O of the core of the electrode assembly.

7c, the arc _A1A2 has a length corresponding to the width D of the segment ₆₁ and has a circumferential angle Φ with respect to the center of the core of the electrode assembly. The circumferential angle Φ can be defined as the angle between two lines connecting both ends of the arc _A1A2 to the center O of the core on a plane perpendicular to the winding axis that passes through _the arc _{A1A2 .}

When the length of _the arc _A1A2 of the segment 61 is the same, the inclination angle Φ decreases as the radius r of the winding turn in which the segment 61 is located increases. Conversely, when the inclination angle Φ of the segment 61 is the same, the length of the arc _A1A2 increases proportionally as the radius r of the winding turn in which the segment ₆₁ is located increases.

The circumferential angle Φ affects the bending quality of the segment 61. In the drawing, the solid arrows indicate the direction of the force applied to bend the segment 61, and the dotted arrows indicate the direction in which the segment 61 is bent. The bending direction is toward the center O of the core.

The circumferential angle Φ of the segment 61 can be 45° or less, preferably 30° or less, depending on the radius r of the winding turn in which the segment 61 is located, in order to improve the uniformity of the folding and prevent the occurrence of cracks.

In one embodiment, the circumferential angle Φ of the segment 61 may increase or decrease gradually or stepwise along the radial direction of the electrode assembly within the above numerical range. In another embodiment, the circumferential angle Φ of the segment 61 may increase gradually or stepwise along the radial direction of the electrode assembly within the above numerical range and then decrease gradually or stepwise, or vice versa. In yet another embodiment, the circumferential angle Φ of the segment 61 may be substantially the same along the radial direction of the electrode assembly within the above numerical range.

Experiments have shown that if the circumferential angle Φ of the segment 61 exceeds 45°, the folding pattern of the segment 61 will not be uniform. The difference in force applied to the center and side edges of the segment 61 will increase, and the pressing of the segment 61 in the circumferential direction will not be uniform. In addition, if the pressing force is increased to ensure uniform folding, cracks may occur in the plain portion 43 near the cut groove 63.

In one example, the circumferential angles Φ of the segments 61 included in the electrode 60 may be substantially identical, and the widths of the segments 61 may increase proportionally as the radius r of the winding turn in which the segments 61 are located increases. By substantially identical, we mean either completely identical or with a deviation of less than 5%.

For example, when the radius of the electrode assembly is 22 mm, the radius of the core is 4 mm, and the segment 61 is disposed from a winding turn located at a radius of 7 mm, if the circumferential angle Φ of the segment 61 is constant at 28.6°, the width D of the segment 61 may increase proportionally according to the radius r of the winding turn in which the segment 61 is located, as shown in Table 1 below. That is, the width of the segment 61 may increase by 0.5 mm at substantially the same rate for every 1 mm increase in the radius r of the winding turn.

Preferably, the width D(r) of the segment 61 located at the winding turn having a radius r with respect to the center O of the core of the electrode assembly can be determined within a range that satisfies the following mathematical formula 1.

[Formula 1]
1≦D(r)≦(2×π×r/360°)×45°
Preferably, each of the plurality of segments 61 may have a width D(r) in the winding direction that gradually or stepwise increases as the radius r of the winding turn in which the segment 61 is located increases with respect to the center of the core of the electrode assembly, or vice versa.

In another embodiment, each of the plurality of segments 61 may have a width D(r) in the winding direction that gradually or stepwise increases in the range of 1 mm to 11 mm as the radius r of the winding turn in which the segment 61 is located increases relative to the center of the core of the electrode assembly, or vice versa.

In yet another embodiment, each of the plurality of segments 61 may have a width D(r) in the winding direction that gradually or stepwise increases and then gradually or stepwise decreases as the radius r of the winding turn in which the segment 61 is located increases relative to the center of the core of the electrode assembly, or vice versa.

In yet another embodiment, each of the plurality of segments 61 may have a width D(r) in the winding direction that gradually or stepwise increases and then gradually or stepwise decreases in the range of 1 mm to 11 mm as the radius r of the winding turn in which the segment 61 is located increases relative to the center of the core of the electrode assembly, or vice versa.

In yet other embodiments, the rate at which the width D(r) of the segment 61 changes as the radius r of the winding turn in which the segment 61 is located increases can be the same or different.

In yet other embodiments, the rate at which the width D(r) of the segment 61 changes from 1 mm to 11 mm as the radius r of the winding turn in which the segment 61 is located increases may be the same or different.

Referring further to FIG. 7b, the height H of the divided pieces 61 may be 2 mm or more. If D2 is less than 2 mm, when the divided pieces 61 are bent toward the core, the divided pieces 61 may not overlap to an extent that sufficient welding strength is ensured, or an empty space (gap) may be generated.

The height H of the segment 61 can be determined by applying the condition that the segment 61 does not block the core when it is bent toward the core. Preferably, the height H of the segment 61 can be adjusted so that 90% or more of the core diameter is open to the outside.

Preferably, the height H of the segment 61 may gradually increase from the core side to the outer periphery depending on the radius of the winding turn in which the segment 61 is located and the radius of the core.

In one example, if the height H of the fractional segment 61 increases stepwise over N stages from h ₁ to h _N as the radius of the winding turn increases, the heights h 1 to h N of the fractional segment 61 can be determined so that the following Equation 2 is satisfied when the _kth height of the fractional segment 61 is _{h k} (k is a natural number from ₁ to N ₎ , the starting radius of the winding turn including the fractional segment 61 having the height h k is r k , and the radius of the core is r _c .

[Formula 2]
2 mm≦h _k ≦r _k −α×r _c (preferably, α is 0.90 to 1)
When the height _hk of the branch piece 61 satisfies the formula 2, even if the branch piece 61 is bent toward the core, 90% or more of the diameter of the core can be opened to the outside.

As an example, the electrode assembly may have a total winding turn radius of 22 mm, with the height of the segment 61 starting at 3 mm, and the height of the segment 61 increasing in order from 3 mm to 4 mm, 5 mm, and 6 mm for each 1 mm increase in the radius of the winding turn including the segment 61, while the remaining winding turns may maintain a substantially constant height of 6 mm. In other words, the radial width of the height-variable section of the segment 61 of the total winding turn radius is 3 mm, and the remaining radius sections correspond to uniform height sections.

In this case, the starting radii _r1 , _r2 , _r3 , and r3 of the winding turn including the segment 61 having heights of 3 mm, 4 mm, 5 mm, and ₆ mm according to the _radius rc of the core of the electrode assembly are as shown in Table 2 below when α is 1 and the equality condition is applied in the inequality on the right side.

When the segment 61 is disposed at the radial position shown in Table 2, the core is not blocked by the segment 61 even if the segment 61 is bent toward the core side. On the other hand, r ₁ , r ₂ , r ₃ , and r ₃ shown in Table 2 can be shifted toward the core side according to the α value. In one example, when α is 0.90, r ₁ , r ₂ , r ₃ , and r ₃ can be shifted toward the core side by 10% of the core radius. In this case, when the segment 61 is bent toward the core side, 10% of the core radius is blocked by the segment 61. r ₁ , r ₂ , r ₃ , and r _{3 shown in Table 2} are limit values of the position where the segment 61 starts. Therefore, the position of the segment 61 can be shifted by a predetermined distance toward the outer periphery from the radius shown in Table 2. FIG. 7d is a diagram showing a schematic diagram of the relationship between the heights _h1 , _h2 , _h3 , and _h4 of the segment 61, the core radius _rc , and the radii _r1 , _r2 , _r3 , and _r3 of the winding turns at which the segment 61 begins to appear.

Referring to Table 2 and FIG. 7d, for example, when the radius r _c of the core C is 3 m, the starting radii r ₁ , r ₂ , r ₃ and r ₄ of the winding turn including the segment 61 having the height of 3 mm (h ₁ ), 4 mm (h ₂ ), 5 mm (h ₃ ) and 6 mm (h _{4 )} may be 6 mm, 7 mm, 8 mm and 9 mm, respectively, and the height of the segment 61 may be maintained at 6 mm from the radius of 9 mm to the last winding turn. Also, the segment 61 may not be included in the winding turn having a radius smaller than 6 mm (r ₁ ). In this example, since the segment 61 having the height of 3 mm (h ₁ ) that is closest to the core C is located from the winding turn having the radius of 6 mm, even if the segment 61 is bent toward the core C, it covers only the radius section from 3 mm to 6 mm and does not substantially block the core C. Depending on the value of α in Equation 2, the position of the segment 61 can be shifted toward the core C within 10% of the core radius r _c .

In other embodiments, the height of the segment 61 may increase at the same or different rates as the starting radius r of the winding turn in which the segment 61 is located increases relative to the center of the core of the electrode assembly.

Preferably, the height H of the segment 61 satisfies formula 2 and the maximum height of the segment 61 can be limited.

FIG. 7e is a conceptual diagram for determining the maximum value h _max for the height H of the segment 61 in the height variable section of the segment 61. As shown in FIG.

Referring to FIG. 7e, in the winding structure of the electrode assembly, the electrode _E1 including the divided piece 61 faces the electrode _E2 of the opposite polarity with the separator S interposed in the radial direction. Both sides of the electrode _E1 are coated with an active material layer E1 _,active , and both sides of the electrode _E2 are also coated with an active material layer E2 _,active . For electrical insulation, the end S _end of the separator S may further extend outward from the end E2 _,end of the electrode _E2 by a length corresponding to the insulating gap W _gap . In addition, the end of the electrode _E1 does not extend outward beyond the end of the electrode _E2 for electrical insulation. Therefore, a section corresponding to the insulating gap W _gap must be secured at the lower end of the non-coating portion 43. In addition, when the electrodes _E1 , _E2 and the separator S are wound, the end S _end of the separator S meanders. Therefore, in order for the division piece 61 to be exposed to the outside of the separator S, a section W _margin,min corresponding to the minimum meandering margin of the separator S must be allocated to the uncoated portion 43. Also, in order to cut the division piece 61, a minimum cutting scrap margin W _scrap,min must be allocated to the end of the current collector foil. Therefore, the maximum height h _max of the division piece 61 in the height variable section of the division piece 61 can be determined by the following Equation 3. In Equation 3, W _foil corresponds to the width of the current collector foil before the current collector foil is cut.

[Formula 3]
h _max = W _foil - W _{scrap, min} - W _{margin, min} - W _gap
Preferably, the insulation gap W _gap may be 0.2 mm to 6 mm when the first electrode is a positive electrode, and the insulation gap W _gap may be 0.1 mm to 2 mm when the first electrode is a negative electrode.

Preferably, the minimum cutting scrap margin W _scrap,min may be 1.5 mm to 8 mm. The minimum cutting scrap margin W _scrap,min may not be assigned depending on the process of forming the divided pieces 61. For example, the cutting grooves 63 may be formed so that the upper edge of the divided pieces 61 coincides with the upper edge of the current collector foil. In this case, W _scrap,min may be 0 in Equation 3.

Preferably, the minimum meandering margin W _{margin, min} of the separation membrane may be 0 to 1 mm.

For example, the minimum cutting scrap margin W _scrap,min may be 1.5 mm, and the minimum meandering margin W _margin,min of the separator S may be 0.5 mm. Under these conditions, when the width W _foil of the current collector foil before forming the divided pieces 61 is 8 mm to 12 mm, and the insulating gap W _gap is 0.6 mm, 0.8 mm, and 1.0 mm, the maximum height h _max of the divided pieces 61 is calculated using Equation 3, and the results are shown in Table 3 below.

Referring to Table 3, the maximum height h _max of the segment 61 in the height variable section of the segment 61 may be set to 10 mm. Thus, the height of the segment 61 in the height variable section of the segment 61 satisfies Equation 2 and may increase stepwise or gradually in the radial direction of the electrode assembly in the range of 2 mm to 10 mm. A design condition in which the height of the segment 61 exceeds 10 mm may cause waviness in the uncoated portion, decreasing the flatness of the uncoated portion. Referring to FIG. 7b further, the separation pitch P of the segment 61 may be adjusted to 0.05 to 1.0 mm. If the separation pitch P is less than 0.05 mm, cracks may occur in the uncoated portion 43 near the bottom of the cut groove 63 due to stress when the electrode 60 travels during a winding process, etc. On the other hand, if the separation pitch P exceeds 1 mm, when the divided pieces 61 are bent, the divided pieces 61 may not overlap to an extent sufficient to ensure sufficient welding strength, or an empty space (gap) may be generated.

On the other hand, when the current collector 41 of the electrode 60 is made of aluminum, it is more preferable to set the separation pitch P to 0.5 mm or more. When the separation pitch P is 0.5 mm or more, even if the electrode 60 runs at a speed of 100 mm/sec or more under a tension of 300 gf or more during a winding process, etc., it is possible to prevent cracks from occurring at the bottom of the cutting groove 63.

According to the experimental results, when the current collector 41 of the electrode 60 is an aluminum foil having a thickness of 15 μm and the separation pitch P is 0.5 mm or more, no cracks occur at the bottom of the cutting groove 63 when the electrode 60 runs under the running conditions described above.

As shown in FIG. 7b, a cut groove 63 is interposed between two adjacent segments 61 in the winding direction (X-axis). The cut groove 63 corresponds to a space created when the plain portion 43 is removed. Preferably, the corners at both ends of the bottom of the cut groove 63 are rounded. That is, the cut groove 63 includes a substantially flat bottom portion 63a and a round portion 63c. The round portion 63c connects the bottom portion 63a and the side edge 63b of the segment 61. In a modified example, the bottom portion 63a of the cut groove 63 may be replaced with an arc shape. In this case, the side edges 63b of the segment 61 may be smoothly connected to each other by the arc shape of the bottom portion 63a.

The radius of curvature of the rounded portion 63c may be greater than 0 and less than 0.5 mm, preferably greater than 0 and less than 0.1 mm, and more preferably 0.01 mm to 0.05 mm. When the radius of curvature of the rounded portion 63c satisfies the above numerical range, it is possible to prevent cracks from occurring at the bottom of the cutting groove 63 while the electrode 60 is traveling during a winding process or the like. If the radius of curvature of the rounded portion 63c exceeds the upper limit of the above numerical range, the space at the bottom of the cutting groove 63 may be reduced, which may have a negative effect on the impregnation of the electrolyte.

The lower interior angle θ of the multiple segment pieces 61 may increase from the core side toward the outer periphery side. As an example, the lower interior angle θ of the multiple segment pieces 61 may increase gradually or in steps from the core side toward the outer periphery side. The lower interior angle θ is the angle between a straight line extending from the bottom 63a of the cutting groove 63 and a straight line extending from the side 53b of the segment piece 61. When the segment piece 61 is symmetrical, the lower interior angle θ on the left and right sides is substantially the same.

As the radius of the electrode assembly increases, the radius of curvature increases. If the lower interior angle θ of the segment 61 increases with the radius of the electrode assembly, the stress generated in the radial and circumferential directions when the segment 61 is bent can be alleviated. Furthermore, if the lower interior angle θ increases, when the segment 61 is bent, the overlapping area with the inner segment 61 and the number of overlapping layers also increase, thereby ensuring uniform welding strength in the radial and circumferential directions and allowing the bent surface area to be formed flat.

Preferably, the lower interior angle θ can be determined by the radius of the winding turn in which the segment 61 is located and the width D of the segment 61.

Figure 7f is a schematic diagram to explain the formula for determining the lower interior angle θ of the segment 61.

Referring to FIG. 7f, ideally, the sides of the segment 61 coincide with the lines AE and DE that connect the two ends A and D of the line segment AD, which corresponds to the width D of the segment 61, to the center E of the core.

When the side of the segment 61 extends in the most ideal direction, the lower interior angle θ _refer of the segment 61 can be approximately determined from the width D of the segment 61 and the radius r of the winding turn in which the segment 61 is located using the following Equation 4, assuming that the line segment EF is approximately equal to the line segments AE and DE.

[Formula 4]

The angle in Equation 4 is an ideal reference angle of the lower interior angle θ _refer of the division segment 61. Meanwhile, a separation pitch P exists between adjacent division segments 61 located in the same winding turn. The length of the separation pitch P is indicated as p. Since the separation pitch P exists between adjacent division segments 61, a tolerance of 50% of the separation pitch P can be given to the lower interior angle θ. That is, the width of the upper end side BC of the division segment 61 can increase by a maximum of p/2 to the upper end side B'C'. The lower interior angle θ' reflecting the tolerance can be expressed by the following Equation 5. The lower interior angle θ _refer is an ideal reference angle ∠BAG, and the lower interior angle θ' is an angle ∠B'AG' reflecting the tolerance due to the separation pitch P. In Equation 5, H corresponds to the height of the division segment 61, and p corresponds to the separation pitch.

[Formula 5]

Preferably, the lower interior angle θ of the segment 61 located at each winding turn of the electrode assembly can satisfy the following formula 6. As a result, when the segment 61 is bent toward the center of the core of the electrode assembly, adjacent segment segments 61 in the circumferential direction do not interfere with each other, allowing for smooth bending.

[Formula 6]

As an example, if the electrode 60 forms a winding structure with a diameter of 22 mm and a core radius of 4 mm, the lower interior angle of the segment 61 may increase gradually or stepwise in the range of 60° to 85° in the height variable section.

As another example, the lower interior angle θ of the multiple segments 61 may increase gradually or stepwise from the core side toward the outer periphery in one or more groups.

On the other hand, the left and right lower interior angles of the segment 61 do not have to be equal. Nevertheless, the lower interior angle θ on at least one side can be designed to satisfy the above-mentioned formula 6.

7a, the width d _B1 of the first portion B1 is designed such that when the third portion B2 is folded toward the core, the core of the electrode assembly is opened outward by 90% or more based on the diameter of the core. The width d _B1 of the first portion B1 may increase in proportion to the folding length of the group 1 of the fractional segments 61. The folding length corresponds to the length from the folding point to the upper end side of the fractional segment 61. Preferably, when the electrode 60 is used to manufacture an electrode assembly for a cylindrical battery of form factor 4680, the width d _B1 of the first portion B1 may be set to 180 mm to 350 mm depending on the diameter of the core of the electrode assembly and the height of the fractional segment 61 included in group 1.

The folding point of the divided piece 61 may be set on a line passing through the bottom of the cutting groove 63 or at a point spaced a predetermined distance above the line. If the divided piece 61 is folded toward the core at a point spaced a predetermined distance from the bottom of the cutting groove 63, the overlapping of the divided pieces in the radial direction becomes easier. When the divided piece 61 is folded, the divided piece on the outside presses the divided piece on the inside based on the center of the core. In this case, if the folding point is spaced a predetermined distance from the bottom of the cutting groove 63, the divided pieces are more easily overlapped as the inner divided piece is pressed in the winding axis direction by the outer divided piece. The separation distance of the folding points may preferably be 1 mm or less. Since the minimum height of the divided piece is 2 mm, the ratio of the separation distance of the folding points to the minimum height may be 50% or less.

In one example, the width of each segment group can be designed to form the same winding turn of the electrode assembly, where the winding turns can be counted relative to the end of the first portion B1 when the electrode 60 is wound.

In other variations, the width of each segment group can be designed to form at least one winding turn of the electrode assembly.

In yet other variations, the width and/or height and/or spacing pitch of the segments 61 belonging to the same segment group may increase or decrease gradually and/or stepwise and/or irregularly within the group or between adjacent groups.

Groups 1 to 8 are merely examples of segment groups included in the third portion B2. The number of groups, the number of segment pieces 61 included in each group, and the width of the groups can be preferably adjusted so that the segment pieces 61 are overlapped in multiple layers to maximize stress distribution during the bending process of the plain portion 43 and ensure sufficient welding strength with the current collector.

In other variations, the height of the second portion B3 may decrease gradually or in steps, similar to the first and second embodiments.

In yet another variation, the division structure of the third portion B2 can be extended to the second portion B3 (see dotted line). In this case, the second portion B3 can also include multiple division segments, similar to the third portion B2. Preferably, the division structure of the second portion B3 can be substantially identical to the outermost division segment group of the third portion B2. In this case, the division segments included in the second portion B3 and the third portion B2 can have substantially the same width, height and spacing pitch. As a variation, the division segments of the second portion B3 can have a width and/or height and/or spacing pitch greater than those of the third portion B2. Alternatively, the final one winding turn of the second portion B3 can be in a form in which the division segments have been removed.

In the third portion B2, the sections (groups 1 to 7) in which the height of the segments 61 increases stepwise based on the winding direction of the electrode 60 can be defined as segment height variable sections, and the final segment group (group 8) can be defined as a uniform height section in which the height of the segments is maintained uniform.

That is, in the third portion B2, when the height of the divisional segments 61 increases stepwise from _h1 to _hN , a section in which the divisional segments 61 having heights _h1 to hN _-1 (N is a high index and a natural number of 2 or more) are arranged corresponds to a height variable section, and a section in which the divisional segments 61 having a height of _hN are arranged corresponds to a height uniform section. The ratio of the height variable section and the height uniform section with respect to the length of the electrode 60 in the winding direction will be described later with reference to a specific embodiment.

When the electrode 60 is used to manufacture an electrode assembly for a cylindrical battery of form factor 4680, the width d _B1 of the first portion B1 may be 180-350 mm. The width of group 1 may be 35-40% of the width of the first portion B1. The width of group 2 may be 130-150% of the width of group 1. The width of group 3 may be 120-135% of the width of group 2. The width of group 4 may be 85-90% of the width of group 3. The width of group 5 may be 120-130% of the width of group 4. The width of group 6 may be 100-120% of the width of group 5. The width of group 7 may be 90-120% of the width of group 6. The width of group 8 may be 115-130% of the width of group 7. The width d _B3 of the second portion B3 may be 180-350 mm, similar to the width of the first portion B1.

In an embodiment, the widths of groups 1 to 8 do not show a uniform increase or decrease pattern. This is because, although the width of the segments gradually increases from group 1 to group 8, the number of segments included in a group is limited to an integer number, and the thickness of the electrode has a slight deviation in the winding direction. Therefore, the number of segments may decrease in a particular segment group. Therefore, the width of the group may show an irregular change from the core side to the outer periphery side, as in the above example. Of course, it is also possible to design the widths of groups 1 to 8 to show a uniform increase pattern by decreasing the width of the segments.

In other words, when the winding direction widths of three consecutively adjacent segment groups in the circumferential direction of the electrode assembly are W1, W2, and W3, respectively, the combination of segment groups may include those in which W3/W2 is smaller than W2/W1.

In the specific example given above, groups 4 to 6 fall into the above case. The width ratio of group 5 to group 4 is 120-130%, and the width ratio of group 6 to group 5 is 100-120%, which is smaller than 120-130%.

According to yet another modification, when the uncoated portion 43 of the electrode 60 has a plurality of segment groups, the segment groups Gk _-1 , _Gk , and Gk ₊₁ may be spaced apart from one another in the winding direction (X-axis) with an inter-group spacing Db therebetween, as shown in Fig. 7g. The height of the uncoated portion corresponding to the inter-group spacing Db may be substantially the same as that of the first portion B1 or the second portion B3.

In one embodiment, from the core side toward the outer periphery, the width D in the winding direction of the segment 61 belonging to each segment group increases stepwise for each group, the height H of the segment 61 also increases stepwise for each group, and the lower interior angle θ can also increase stepwise for each group.

In other embodiments, the winding width Dg of the segment group may increase gradually or stepwise from the core side toward the outer periphery. The winding width Dg may increase for each segment group or may increase for two or more segment groups.

In yet another embodiment, the spacing between the segment groups (inter-group spacing Db) may increase gradually or stepwise from the core side toward the outer periphery. The inter-group spacing Db may increase for each segment group, or may increase for two or more segment groups.

By adjusting the winding direction width Dg of the segment group and the group spacing Db, the segment 61 is radially arranged in a certain region to form one or more segment alignment portions 61g, as shown in Figures 7h and 7i. The segment alignment portion 61g is a collection of segment groups Gk _-1 , _Gk , and Gk ₊₁ aligned along the radial direction of the electrode assembly JR.

As shown in FIG. 7j, when lines are connected between both ends of the segment groups G _k−1 , G _k , and G _k+1 included in the segment alignment unit 61g and the center O of the core C, each segment group forms a fan shape.

Preferably, the sector shapes of the segment groups G _k-1 , G _k , and G _k+1 included in the segment alignment unit 61g may be substantially identical in the magnitude of the circumferential angle δ and the range of the circumferential angle δ. If there is a thickness tolerance in the electrodes, the sector shapes of the segment groups G _k -1 , G _k , and G _k+1 included in the segment alignment unit 61g may be substantially identical in the magnitude of the circumferential angle δ and may differ in the range of the circumferential angle δ.

The inscribed angle δ can be 20° or more, optionally 25° or more, optionally 30° or more, optionally 35° or more, or optionally 40° or more.

When the segment 61 included in the segment alignment portion 61g is folded onto the core C, a folded surface region F is formed on a plane that is approximately perpendicular to the winding axis, as shown in Figures 7h and 7i. In addition, an electrolyte-impregnated portion Ep is formed between adjacent folded surface regions F in the circumferential direction.

Since the electrolyte-impregnated portion Ep does not have a bent structure of the divided pieces 61, the ends of the separation membrane and the active material layer of the electrode are exposed to the outside when viewed from the winding axis direction (i.e., the direction in which the electrolyte is injected). Therefore, when the electrolyte is injected from the winding axis direction of the electrode assembly JR, the electrolyte quickly penetrates into the electrode assembly JR while in direct contact with the ends of the separation membrane and the active material layer, improving the electrolyte impregnation speed.

Also, as described above with reference to FIG. 7a, in order to further improve the electrolyte impregnation speed, it is preferable that the widthwise end SL of the separation membrane SP is separated from the reference line DL by a distance that corresponds to 30% or less of the minimum segment height Ha. In this case, the electrolyte is also impregnated through the bottom of the cut groove 63, which further improves the electrolyte impregnation speed and improves the uniformity of the electrolyte impregnation.

7h is an example of a structure in which the folded surface regions F are arranged at 90° intervals, and FIG. 7i is an example of a structure in which the folded surface regions F are arranged at 180° intervals. Here, the arrangement angle of the folded surface region F may be defined as the angle between straight lines passing through the geometric center of a figure that approximately corresponds to the peripheral shape of the folded surface region F. That is, when a line connecting the center of the core of the electrode assembly and the geometric center of a figure that approximately corresponds to the folded surface region F is defined as an angle measurement line, an angle measured using the angle measurement lines of adjacent folded surface regions F in the circumferential direction may be regarded as the arrangement angle of the folded surface region F. As an example, the geometric center of a figure that corresponds to the peripheral shape of the folded surface region F may be the center of gravity.

The segment groups constituting the folded surface region F may be arranged radially from the center of the core of the electrode assembly JR. The uncoated portions of the wound turn portions constituting the electrolyte-impregnated portion Ep may also be arranged radially from the center of the core of the electrode assembly JR. The circumferential length of the segment groups included in the folded surface region F may gradually increase from the core toward the outer periphery. The uncoated portions of the wound turn portions constituting the electrolyte-impregnated portion Ep also increase in circumferential length from the core toward the outer periphery. The figure formed by the periphery of the folded surface region F is generally similar to a sector with the central portion removed.

The electrode assembly JR shown in Figure 7h is suitable for welding a collector with four welding areas designed radially at 90° intervals, and the electrode assembly JR shown in Figure 7i is suitable for welding a collector with two welding areas designed radially at 180° intervals.

In the embodiment, a structure in which there are four folded surface areas F (welded areas) spaced at 90° intervals or two folded surface areas F spaced at 180° intervals is illustrated, but the present invention is not limited to these. For example, various radial arrangements are possible, such as 12 folded surface areas spaced at 30° intervals, 8 folded surface areas spaced at 45° intervals, 6 folded surface areas spaced at 60° intervals, 5 folded surface areas spaced at 72° intervals, and 3 folded surface areas spaced at 120° intervals.

In other variations, the folded surface regions F may not be arranged radially, but may be formed in various patterns at positions corresponding to the areas where welding of the current collector is performed. The folded surface regions F may be in the form of geometric figures such as a square, a rectangle, a parallelogram, a trapezoid, etc. Such various shapes of the folded surface regions F may be determined by adjusting the width Dg of the segment groups in the winding direction and the spacing Db between the segment groups.

On the other hand, when the segment groups are spaced apart along the winding direction (X-axis) and designed so that folded surface regions F are not formed in some areas, the segment groups may be misaligned from the core toward the outer periphery due to electrode thickness tolerances. Such misalignment of the segment groups accumulates as one moves toward the outer periphery turns.

According to one embodiment of the present invention, in order to ensure an area in which the current collector can be welded even if misalignment of the segment groups accumulates as one moves toward the outer periphery, the width of the segment groups increases gradually or in stages from the core toward the outer periphery, resulting in the formation of a fan-shaped folded surface area F.

Therefore, even if the misalignment of the segment groups accumulates toward the outer periphery and the shape of the folded surface region F is deformed (see FIG. 7i, as the electrode assembly is wound clockwise, the shape of the folded surface region F is also deformed clockwise), the predetermined welding area w can still be sufficiently secured, as can be seen from the deformed area indicated by the arrow in FIG. 7i.

The circumferential angle of the sector shape in which the folded surface region F is formed (see δ in FIG. 7j) can be determined by the amount of accumulated misalignment. In the embodiment, a sector shape having a circumferential angle of about 30° is illustrated. The larger the circumferential angle of the sector shape, the greater the allowable accumulated amount of misalignment. On the other hand, the area of the electrolyte-impregnated portion Ep in which the folded surface region F is not formed decreases.

On the other hand, if the area corresponding to the width of the segment group is made up of one segment, the larger the circumferential angle of the fan shape corresponding to the folding surface region F, the more deformation occurs in the circumferential direction when folding the segment, making it difficult to fold smoothly. Therefore, in one embodiment of the present invention, when the folding surface region F is designed to be fan-shaped, the plain section of the winding turn region corresponding to the fan shape is formed from a segment group, and each segment belonging to the corresponding group is folded to allow the folding process of the plain section to be performed smoothly.

According to the embodiment, if the circumferential angle of the winding turn portion located within the sector shape corresponding to the folded surface region F exceeds 30°, the plain portion of the winding turn portion is divided into at least two or more segments, and the circumferential angle of the winding turn portion corresponding to each segment is set to 30° or less.

In one embodiment of the present invention, the shape of the segment 61 can be varied in various ways.

Figure 8a is a plan view showing the structure of an electrode 70 according to a fifth embodiment of the present invention.

Referring to FIG. 8a, the electrode 70 of the fifth embodiment has substantially the same configuration as the above-described embodiment, except that the shape of the segment 61' is different. Therefore, unless otherwise specified, the configuration of the fourth embodiment can be similarly applied to the fifth embodiment.

The segment 61' has a geometric shape in which the width at the top and the width at the bottom are approximately the same. Preferably, the segment 61' may be rectangular.

The corners, or vertices, of the square shape can be rounded or chamfered like a chamfer rather than having sharp edges.

Figure 8b shows the definition of the width, height and spacing pitch of the rectangular segment 61'.

Referring to FIG. 8b, the width D, height H and spacing P of the divided segments 61' are set to sufficiently increase the number of overlapping layers of the plain portion 43 to prevent the plain portion 43 from breaking during bending and to improve the welding strength with the current collector, and to prevent abnormal deformation of the plain portion 43. Abnormal deformation refers to the plain portion below the bending point collapsing and deforming irregularly, as it is unable to maintain a straight state.

The width D of the segment 61' is defined as the length between two points where two straight lines extending from both sides of the segment 61' intersect with a straight line extending from the bottom 63a of the cut groove 63. The height H of the segment 61' is defined as the shortest distance between the top edge of the segment 61' and a straight line extending from the bottom 63a of the cut groove 63. The separation pitch P of the segment 61' is defined as the length between two points where a straight line extending from the bottom 63a of the cut groove 63 intersects with a straight line extending from the two side edges 63b connected to the bottom 63a. When the side edges 63b and/or the bottom edge 63a are curved, the straight line may be replaced by a tangent line extending from the intersection of the side edges 63b and the bottom edge 63a to the side edges 63b and/or the bottom edge 63a.

The conditions regarding the width D, height H, and separation pitch P of the segment 61' are preferably substantially the same as those in the fourth embodiment described above, and therefore will not be described again. However, since the segment 61' is rectangular, the lower interior angle of the segment 61' may be a constant 90°.

Also, in the electrode 70 according to the fifth embodiment, as shown in Fig. 8c, a plurality of segment groups Gk _-1 , _Gk , and Gk ₊₁ may be arranged in the winding direction (X-axis) with a spacing Db therebetween. In this case, the embodiments described above with reference to Figs. 7h, 7i, and 7j may be substantially similarly applied to an electrode assembly manufactured by winding the electrode 70 shown in Fig. 8c. That is, the only difference is that the shape of the segment included in the segment group is changed from a trapezoid to a rectangle, and the other features may be substantially similarly applied to the embodiments described with reference to Figs. 7h, 7i, and 7j.

When the third part B2 and the second part B3 include multiple segments 61, 61' as in the fourth and fifth embodiments, the shape of each segment 61, 61' can be varied in various ways.

Preferably, the segments can be deformed in various forms while satisfying at least one of the following conditions:

Condition 1: The width at the bottom is wider than the width at the top.

Condition 2: The width of the bottom and the width of the top are equal.

Condition 3: The width remains the same from bottom to top.

Condition 4: The width decreases from bottom to top.

Condition 5: The width decreases and then increases from bottom to top.

Condition 6: The width increases and then decreases from bottom to top.

Condition 7: The width increases from bottom to top and then remains constant.

Condition 8: The width decreases from bottom to top and then remains constant.

Condition 9: The interior angles on one side of the lower part are the same as the interior angles on the other side.

Here, the interior angle may be defined as the angle between the side of the segment and the width direction of the bottom of the segment. If the side is curved, the interior angle is defined as the angle between the tangent drawn at the lowest point of the curve and the width direction of the bottom of the segment.

Condition 10: The interior angles on one side of the lower part are different from the interior angles on the other side.

Condition 11: The interior angle on one side of the lower part and the interior angle on the other side of the lower part are each an acute angle, a right angle, or an obtuse angle.

Condition 12: Symmetrical with respect to the winding axis direction.

Condition 13: Asymmetrical with respect to the winding axis direction.

Condition 14: The sides are straight.

Condition 15: The sides are curved.

Condition 16: The sides are convex outward.

Condition 17: The sides are convex toward the inside.

Condition 18: The upper and/or lower corners are constructed so that straight lines intersect.

Condition 19: The upper and/or lower corners are structured as straight lines and curves intersecting.

Condition 20: The upper and/or lower corners are curved structures.

Condition 21: The top and/or bottom corners are rounded.

Figure 9 shows an example of the shape of a segment according to a modified embodiment of the present invention.

As shown in the figure, the segment may have various geometric shapes with the dotted line connecting the bottoms of the cut grooves on both sides as its base. The geometric shape has a structure in which at least one straight line, at least one curved line, or a combination of these are connected. As an example, the segment may have a polygonal shape, a rounded pattern, or various shapes that combine these.

Specifically, the segments may be symmetrical trapezoidal (circle a); asymmetrical trapezoidal (circle b); parallelogram (circle c); triangular (circle l); pentagonal (circle k); arc-shaped (circle e); or elliptical (circle f).

The shape of the segments is not limited to that shown in FIG. 9, and may be modified to other polygonal shapes, other round shapes, or combinations thereof, so long as it satisfies at least one of the above conditions 1 to 21.

In the polygonal shapes of the segments circle a, circle b, circle c, circle k and circle l, the upper corners and/or lower corners may be straight line intersections or rounded (see enlargement of the upper and lower corners of circle a).

In the polygonal shapes of the segments a, b, c, k, and l and the round shapes of the segments e and f, the interior angle _θ1 on one side of the lower part and the interior angle _θ2 on the other side can be the same or different, and the interior angle _θ1 on one side of the lower part and the interior angle _θ2 on the other side can be acute angles, right angles, or obtuse angles, respectively. The interior angle is the angle between the base and the side of the geometric figure. When the side is curved, the straight line can be replaced by a tangent extending from the intersection of the base and the side.

The shape of the sides of a polygonal segment can be varied in many ways.

As an example, the side of the segment circle a can be transformed into a curve that bulges outward, as in circle d, or into a curve that is concave inward, as in circle g or circle j.

As another example, the side of the segment with the shape of a circle a can be transformed into a broken line that is concave inwardly of the segment, as in the shapes of a circle h or circle i. Although not shown, the side of the segment with the shape of a circle a can be transformed into a broken line that bulges outwardly.

In the shapes of the segments having variously modified sides, circle d, circle g, circle j, circle h, and circle i, the interior angle _θ1 on one side of the lower portion and the interior angle _θ2 on the other side may be the same or different, and the interior angle _θ1 on one side of the lower portion and the interior angle _θ2 on the other side may be an acute angle, a right angle, or an obtuse angle, respectively.

The width of the segments may vary from bottom to top.

As one example, the width of the portion may be maintained constant from the bottom to the top (form circle c). As another example, the width of the portion may gradually decrease from the bottom to the top (form circle a, circle b, circle d, circle e, circle f, and circle g). As yet another example, the width of the portion 61 may gradually decrease and then increase from the bottom to the top (form circle i and circle j). As yet another example, the width of the portion may gradually increase and then decrease from the bottom to the top (form circle k). As yet another example, the width of the portion may gradually decrease from the bottom to the top and then remain constant (form circle h). Although not shown, the width of the portion may gradually increase from the bottom to the top and then remain constant.

Meanwhile, among the segment shapes exemplified in FIG. 9, polygonal shapes with flattened upper portions may be rotated 180°. As an example, when the segment shape circle a, circle b, circle d, or circle g is rotated 180°, the width of the segment may gradually increase from the bottom to the top. As another example, when the segment shape circle h is rotated 180°, the width of the segment may remain constant from the bottom to the top and then gradually increase.

In the above-described embodiment (variant), according to another aspect of the present invention, it is also possible to change the shape of the segments 61, 61' along the region of the third portion B2. As an example, a round shape (e.g., semicircle, semiellipse, etc.) that is advantageous for stress dispersion can be applied to the section where stress is concentrated, and a polygonal shape with the largest possible area (e.g., rectangle, trapezoid, parallelogram, etc.) can be applied to the section where stress is relatively low.

In yet another embodiment, the multiple segments may have different shapes individually, in groups, or in two or more groups along a direction parallel to the winding direction of the electrode assembly.

In the above-described embodiment (variant), the division structure of the third part B2 may also be applied to the first part B1. However, if the division structure is applied to the first part B1, when the division pieces 61, 61' of the third part B2 are bent due to the curvature radius of the core, a reverse forming phenomenon may occur in which the end of the first part B1 is bent toward the outer periphery. Therefore, it is preferable not to apply the division structure to the first part B1, or, even if the division structure is applied, to adjust the width and/or height and/or spacing pitch of the division pieces 61, 61' to a small level at which reverse forming does not occur, taking into account the curvature radius of the core.

The height of the segment at which reverse forming may occur may be less than about 3 mm. If the height of the segment is less than 2 mm, the segment may interfere with the separator, making it difficult to bend. If the height of the segment is less than 4 mm, the welding process of the segment may not be performed smoothly. Preferably, the minimum height _Hmin of the segment designed for bending may be 5 mm.

8a and 9a, when the end SL in the width direction of the separator is within ±30% of the height Ha of the smallest segment among the segments having a height equal to or greater than the minimum height _Hmin (e.g., 2 mm, 3 mm, 4 mm, or 5 mm) that can be folded in the plain portion with reference to the reference line DL, the impregnation can be significantly improved. That is, when determining the smallest segment that defines the position of the end SL in the width direction of the separator, segments that may be subject to reverse forming or segments that are not folded can be excluded.

From another perspective, when the end SL in the width direction of the separator is within a range of ±30% of the greater of the minimum fragment height Ha in the uncoated portion and the minimum height _Hmin at which the separator can be bent, {max(Ha, _Hmin )}, based on the reference line DL, the impregnation property can be significantly improved.

From another perspective, the impregnation of the electrolyte can be significantly improved if the end SL in the width direction of the separator is within a range of ±30% of the minimum height _Hmin at which the separator can be bent with respect to the reference line DL. This range may be within the range of the reference line DL ±1.5 mm, the reference line DL ±1.2 mm, the reference line DL ±0.9 mm, or the reference line DL ±0.6 mm.

In accordance with yet another aspect of the present invention, after the electrodes 60, 70 are wound into an electrode assembly, the exposed segments on the upper and lower sides of the electrode assembly may overlap in multiple layers along the radial direction of the electrode assembly to form a folded surface region.

It should be made clear that the following description of the folded surface area can be applied in a substantially similar manner to the folded surface area formed as the segments of the segment alignment section are folded.

Figure 10a is a schematic diagram showing a cross section of a folded surface region F formed when a segment 61 is folded toward the core C of the electrode assembly 80. In Figure 10a, the cross section of the folded surface region F is shown only on the left side based on the winding axis of the electrode assembly 80. The folded surface region F may be formed on both the upper and lower parts of the electrode assembly 80. Figure 10b is a perspective view showing a schematic view of an electrode assembly 80 in which a folded surface region F is formed.

10a and 10b, the folded surface region F has a structure in which the split segments 61 are stacked in multiple layers in the winding axis direction. The stacking direction is the winding axis direction (Y axis). Section circle 1 is a split segment-free section (first part B1) where there are no split segments, and sections circle 2 and circle 3 are sections where winding turns including split segments are located. Section circle 2 is a height-variable section where the height of the split segments 61 varies, and section circle 3 is a height-uniform section where the height of the split segments is uniform up to the outer periphery of the electrode assembly. As will be described later, the radial lengths of section circle 2 and section circle 3 may vary. Meanwhile, the uncoated portion (second part B3) included in at least one winding turn including the outermost winding turn may not include a split segment structure. In this case, section circle 3 may be excluded from second part B3.

In section 2, the height of the segment 61 may vary stepwise from a minimum height _h1 (= _hmin ) to a maximum height _hN (= _hmax ) in a section of radii _r1 to _rN of the electrode assembly 80. The height variable section in which the height of the segment 61 varies is _r1 to _rN . From radius _rN to radius R of the electrode assembly 80, the height of the segment 61 is uniformly maintained at _hN . A uniform height means that the deviation in height is within 5%.

At any radial position in section circle 2 and section circle 3, the number of stacked segments 61 varies depending on the radial position. Also, the number of stacked segments 61 can vary depending on the width of section circle 2, the minimum height _h1 and maximum height _hN of the segment 61 in the height variable section, and the height change amount Δh of the segment 61. The number of stacked segments 61 is the number of segment segments that intersect with an imaginary line drawn from any radial position of the electrode assembly 80 in the winding axis direction.

Preferably, the number of layers of the segment 61 at each position of the folded surface region F can be optimized to match the required welding strength of the current collector by adjusting the height, width, and spacing pitch of the segment 61 according to the radius of the winding turn in which the segment 61 is included.

First, a specific example will be given to explain how the number of layers of the segment 61 changes along the radial direction of the folded surface area F as the maximum height _hN of the segment 61 changes when the minimum height _h1 of the segment 61 is the same in the height variable section (circle 2) of the segment 61.

Electrode assemblies of Examples 1-1 to 1-7 were prepared. The electrode assemblies of the examples have a radius of 22 mm and a core diameter of 4 mm. The positive and negative electrodes included in the electrode assemblies have the electrode structure shown in FIG. 7a. That is, the shape of the segments is trapezoidal. The second part B3 of the positive and negative electrodes does not include the segments. The length of the second part B3 is 3% to 4% of the total length of the electrode. The positive and negative electrodes and the separator were wound by the method described with reference to FIG. 2. The number of winding turns is between 48 turns and 56 turns, but the number of winding turns in the examples is 51 turns. The thicknesses of the positive and negative electrodes are 149 μm, 193 μm and 13 μm, respectively. The thicknesses of the positive and negative electrodes include the thickness of the active material layer. The thicknesses of the positive and negative electrode collectors are 15 μm and 10 μm, respectively. The lengths of the positive and negative electrodes in the winding direction are 3948 mm and 4045 mm, respectively.

In each example, the variable height section (circle 2) of the segment 61 was set to a minimum height of 3 mm so that it began at a radius of 5 mm. In each example, the height of the segment 61 was increased by 1 mm for every 1 mm increase in radius, and the maximum height of the segment 61 was varied from 4 mm to 10 mm.

Specifically, in Example 1-1, the height variable section (circle 2) of the minute segment 61 is 5 mm to 6 mm, and the height of the minute segment 61 varies from a radius of 3 mm to 4 mm. In Example 1-2, the height variable section (circle 2) of the minute segment 61 is 5 mm to 7 mm, and the height of the minute segment 61 varies from 3 mm to 5 mm. In Example 1-3, the height variable section (circle 2) of the minute segment 61 is 5 mm to 8 mm, and the height of the minute segment 61 varies from 3 mm to 6 mm. In Example 1-4, the height variable section (circle 2) of the minute segment 61 is 5 mm to 9 mm, and the height of the minute segment 61 varies from 3 mm to 7 mm. In Example 1-5, the height variable section (circle 2) of the minute segment 61 is 5 mm to 10 mm, and the height of the minute segment 61 varies from 3 mm to 8 mm. In Example 1-6, the height variable section (circle 2) of the segment 61 is 5 mm to 11 mm, and the height of the segment 61 varies from 3 mm to 9 mm. In Example 1-7, the height variable section (circle 2) of the segment 61 is 5 mm to 12 mm, and the height of the segment 61 varies from 3 mm to 10 mm. In Examples 1-1 to 1-7, the height of the segment 61 is uniform from the radius corresponding to the upper limit of the height variable section (circle 2) to the outer periphery. As an example, in Example 1-7, the height of the segment 61 is uniform at 10 mm from a radius of 12 mm to 22 mm. Meanwhile, the electrode assembly of the comparative example maintains the height of the segment 61 at a single height of 3 mm from a radius of 5 mm to a radius of 22 mm.

Figure 10c is a graph showing the results of counting the number of stacked segments along the radial direction in the folded surface region F of the positive electrode formed on the upper part of the electrode assembly according to Examples 1-1 to 1-7 and the comparative example. Substantially the same results are shown in the folded surface region of the negative electrode. The horizontal axis of the graph is the radius based on the center of the core, and the vertical axis of the graph is the number of stacked segments counted at each radius point. The same is true for Figures 10d and 10e described below.

Referring to FIG. 10c, a uniform number of stacks section b1 of the divided segment appears in common in Examples 1-1 to 1-7 and Comparative Example 1. The uniform number of stacks section b1 is a radial section of a flat region in each graph. The length of the uniform number of stacks section b1 increases as the maximum height of the divided segment decreases, and the uniform number of stacks section b1' of the comparative example is the longest. Meanwhile, the number of stacks of the divided segment increases as the maximum height _hN of the divided segment increases. That is, if the maximum height _hN of the divided segment increases and the width of the height variable section (circle 2) of the divided segment increases, the number of stacks of the divided segment increases, while the width of the uniform number of stacks section b1 decreases. Outside the uniform number of stacks section b1, a number of stacks decreasing section b2 appears in which the number of stacks of the divided segment decreases as the radius increases. The number of stacks decreasing section b2 is a radial section in which the number of stacks of the divided segment decreases as the radius of the electrode assembly increases. The uniform number of stacks section b1 and the number of stacks decreasing section b2 are adjacent to each other in the radial direction and are complementary to each other. That is, as the length of one section increases, the length of the other section decreases. In the stack number decreasing section b2, the amount of decrease in the stack number is proportional to the distance from the stack number uniform section b1.

In terms of the number of layers of the segment, in Examples 1-1 to 1-7, the number of layers of the segment in the uniform layer number section b1 is 10 or more. The area where the number of layers of the segment is 10 or more can be set as a preferred welding target area. The welding target area is the section where at least a portion of the current collector is welded.

In Examples 1-1 to 1-7, the uniform number of layers section b1 begins at the radius where the variable height section (circle 2) of the segment begins. In other words, the variable height section (circle 2) begins at a radius of 5 mm and extends toward the outer periphery.

The following Table 4 shows the results of calculating the ratio of the length of the segment-free section (c, circle 1 in FIG. 10a) to the radius (b-a) of the electrode assembly excluding the core for the positive electrode in Examples 1-1 to 1-7 and Comparative Example 1, the ratio (e/f) of the length of the uniform number of stacks section b1 to the length (f) from the radius point (5 mm) where the uniform number of stacks section begins to the outermost point (22 mm) of the electrode assembly, the ratio (d/f) of the length of the variable height section (d) of the segment to the length (f) from the radius point (5 mm) where the uniform number of stacks section begins to the outermost point (22 mm) of the electrode assembly, the ratio (h) of the length of the electrode region corresponding to the segment-free section (first part B1) to the entire length of the electrode, the ratio (i) of the length of the electrode region corresponding to the variable height section to the entire length of the electrode, and the ratio (i) of the electrode region corresponding to the uniform height section to the entire length of the electrode.

The negative electrode has substantially the same parameters as the positive electrode, except for a difference of 0.1 to 1.2% in parameter h. The sum of the ratios h, i, and j is slightly different from 100%. This is because there is a section without a segment in the second part B3, which corresponds to the outer peripheral uncoated part of the electrode. For example, in the case of Example 1-1, there is no segment in the second part B3, which corresponds to about 4% of the total length of the electrode. In Table 4, a to f are parameters based on the radial length, and h, i, and j are parameters based on the longitudinal direction of the electrode before it is wound into an electrode assembly. In addition, the parameters corresponding to the ratio (%) are values rounded off to the nearest tenth. These are substantially the same in Tables 5 and 6 described below.

With reference to Examples 1-1 to 1-7 in Table 4, the number of layers of the segment is 11 to 26, and the ratio (d/f) of the height variable section (d) to the radius section (f) containing the segment is 6% to 41%. The ratio (e/f) of the uniform number of layers section (e) to the radius section (f) containing the segment is 47% to 82%. The ratio (c/(b-a)) of the segment-omitted section (c, circle 1 in Figure 10a) to the radius (b-a) of the electrode assembly excluding the core is 15%. The ratio of the length of the electrode region corresponding to the segment-omitted section (first part B1) to the entire length of the electrode is 6%, the ratio of the length of the electrode region corresponding to the height variable section to the entire length of the electrode is 3% to 32%, and the ratio of the length of the electrode region corresponding to the uniform height section to the entire length of the electrode is 59% to 87%. The number of layers (g) in the uniform number of layers section is 10 or more in all of Examples 1-1 to 1-7. The number of layers in the uniform number of layers section (e) decreases as the height variable section (d) of the divided segment increases, but the number of layers (g) of the divided segment increases in the uniform number of layers section (e). Preferably, the uniform number of layers section (e) where the number of layers (g) of the divided segment is 10 or more can be set as a welding target area.

Cylindrical batteries having 1865 and 2170 form factors have an electrode assembly radius of about 9 mm to 10 mm. Therefore, for conventional cylindrical batteries, the radial length of the segment section (f) cannot be secured at 17 mm, as in Examples 1-1 to 1-7, and the length of the uniform stacking number section (e) where the number of segment stacks is 10 or more cannot be secured at 8 mm to 14 mm. This is because, in conventional cylindrical batteries, if the core radius is designed to be 2 mm as in Examples 1-1 to 1-7, the radius section in which the segment can be arranged is substantially only 7 mm to 8 mm. In addition, in conventional cylindrical batteries, the length of the electrode in the winding direction is about 600 mm to 980 mm. Such a short electrode length is only about 15% to 24% of the length of the electrodes used in Examples 1-1 to 1-7 (positive electrode 3948 mm, negative electrode 4045 mm). Therefore, the numerical ranges for parameters h, i, and j cannot be easily derived from the design specifications of conventional cylindrical batteries.

Next, a specific example will be given to explain how the number of layers of the segment changes along the radial direction of the folded surface area F when the maximum height _hN of the segment is the same in the height variable section of the segment (circle 2 in Figure 10a) as the minimum height _h1 of the segment changes.

The electrode assemblies of Examples 2-1 to 2-5 have a radius of 22 mm, and a diameter of the core C of 4 mm. The minimum height _h1 in the height variable section of the segment 61 (circle 2 in FIG. 10a) was the same as 4 mm, and the maximum height _hN was changed in 1 mm increments from 6 mm to 10 mm. Therefore, in the electrode assemblies of Examples 2-1 to 2-5, the widths of the height variable section of the segment (circle 2 in FIG. 10a) were 2 mm, 3 mm, 4 mm, 5 mm, and 6 mm, respectively, and the segment-free section (circle 1 in FIG. 10a) was a radius section from 2 mm to 6 mm.

The electrode assemblies of Examples 3-1 to 3-4 have a radius of 22 mm, and the diameter of the core C is 4 mm. The minimum height _h1 in the height variable section of the segment 61 (circle 2 in FIG. 10a) is the same as 5 mm, and the maximum height _hN is changed in 1 mm increments from 7 mm to 10 mm. Therefore, in the electrode assemblies of Examples 3-1 to 3-4, the widths of the height variable section of the segment (circle 2 in FIG. 10a) are 2 mm, 3 mm, 4 mm, and 5 mm, respectively, and the segment-free section (circle 1 in FIG. 10a) is a radius section from 2 mm to 7 mm.

The electrode assemblies of Examples 4-1 to 4-3 have a radius of 22 mm, and a diameter of the core C of 4 mm. The minimum height _h1 in the height variable section of the segment 61 (circle 2 in FIG. 10a) was the same as 6 mm, and the maximum height _hN was changed in 1 mm increments from 8 mm to 10 mm. Therefore, in the electrode assemblies of Examples 4-1 to 4-3, the widths of the height variable section of the segment (circle 2 in FIG. 10a) were 2 mm, 3 mm, and 4 mm, respectively, and the segment-free section (circle 1 in FIG. 10a) was a radius section from 2 mm to 8 mm.

The electrode assemblies of Examples 5-1 and 5-2 have a radius of 22 mm, and a diameter of the core C of 4 mm. The minimum height _h1 in the height variable section of the segment 61 (circle 2 in FIG. 10a) was the same as 7 mm, and the maximum height _hN was changed in 1 mm increments from 9 mm to 10 mm. Therefore, in the electrode assemblies of Examples 5-1 and 5-2, the widths of the height variable section of the segment (circle 2 in FIG. 10a) were 2 mm and 3 mm, respectively, and the segment-free section (circle 1 in FIG. 10a) was a radius section from 2 mm to 9 mm.

Figure 10d is a graph showing the results of counting the number of stacked pieces measured along the radial direction in the folded surface region F of the positive electrode formed on the upper part of the electrode assembly according to Examples 2-1 to 2-5, Examples 3-1 to 3-4, Examples 4-1 to 4-3, Examples 5-1 and 5-2. Substantially the same results are shown in the folded surface region of the negative electrode.

In FIG. 10d, graph (a) shows the results of counting the number of laminated segments along the radial direction in the folded surface region F for Examples 2-1 to 2-5, graph (b) for Examples 3-1 to 3-4, graph (c) for Examples 4-1 to 4-3, and graph (d) for Examples 5-1 and 5-2.

Referring to FIG. 10d, a uniform number of layers section b1 of the sub-segment appears in common to all examples. The uniform number of layers section b1 is a radius section of a flat region in the graph. When the minimum height _h1 of the sub-segment is the same, the length of the uniform number of layers section b1 increases as the maximum height _hN of the sub-segment decreases. In addition, when the maximum height _hN of the sub-segment is the same, the length of the uniform number of layers section b1 increases as the minimum height _h1 of the sub-segment decreases. Meanwhile, in the uniform number of layers section b1, the number of layers of the sub-segment increases as the maximum height _hN of the sub-segment increases. In the examples, a decreasing number of layers section b2 appears adjacent to the uniform number of layers section b1.

In the embodiment, the number of layers of the segment in the uniform layer number section b1 is 10 or more. Preferably, the area where the number of layers of the segment is 10 or more can be set as a preferred welding target area.

In the examples, the uniform number of layers section b1 starts at the radius point where the variable height section of the segment (circle 2 in FIG. 10a) starts. In examples 2-1 to 2-5, the variable height section of the segment (circle 2 in FIG. 10a) starts at 6 mm and extends to the outer periphery. In examples 3-1 to 3-4, the variable height section of the segment (circle 2 in FIG. 10a) starts at 7 mm and extends to the outer periphery. In examples 4-3 to 4-3, the variable height section of the segment (circle 2 in FIG. 10a) starts at 8 mm and extends to the outer periphery. In examples 5-1 and 5-2, the variable height section of the segment (circle 2 in FIG. 10a) starts at 9 mm and extends to the outer periphery.

Table 5 below shows the results of calculating various parameters for Examples 2-1 to 2-5, Examples 3-1 to 3-4, Examples 4-1 to 4-3, Examples 5-1 and 5-2, including the ratio (e/f) of the length of the uniform stacking number section to the length from the radius point (6 mm, 7 mm, 8 mm, 9 mm) where the uniform stacking number section begins to the outermost point (22 mm) of the electrode assembly, and the ratio (d/f) of the length of the height-variable section (circle 2) of the segment to the length from the radius point (6 mm, 7 mm, 8 mm, 9 mm) where the uniform stacking number section begins to the outermost point (22 mm) of the electrode assembly.

10a and 10d, the maximum height _hN of the segment in the height variable section (circle 2) of the segment is the same at 10 mm, but the minimum height _h1 of the segment increases by 1 mm to 4 mm, 5 mm, 6 mm, and 7 mm, and the length of the height variable section (circle 2) decreases by 1 mm to 6 mm, 5 mm, 4 mm, and 3 mm. In the four examples, the ratio (e/f) of the uniform number of layers section is the highest in Example 2-5 at 69% and the lowest in Example 5-2 at 38%, and the number of layers in the uniform number of layers section is all the same. From the results shown in Table 5, it can be seen that when the maximum height _hN of the segment is the same, the minimum height _h1 of the segment decreases, and as the width of the height variable section (circle 2) of the segment increases, the width of the uniform number of layers section also increases proportionally. The reason is that as the minimum length _h1 of the segment is smaller, the radial point where the segment starts is closer to the core side, and the area where the segment is laminated is expanded toward the core side.

Referring to Table 5, it can be seen that the number of layers of the segment is 16 to 26, the ratio (d/f) of the segment height variable section (circle 2) is 13% to 38%, and the ratio (e/f) of the uniform number of layers section is 31% to 69%. In addition, the ratio (c/(b-a)) of the segment-omitted section (circle 1) to the radius (b-a) of the electrode assembly excluding the core is 20% to 35%. In addition, the ratio of the length of the electrode region corresponding to the segment-omitted section (circle 1) to the entire length of the electrode is 10% to 20%, the ratio of the length of the electrode region corresponding to the height variable section (circle 2) to the entire length of the electrode is 6% to 25%, and the ratio of the length of the electrode region corresponding to the uniform height section (circle 3) to the entire length of the electrode is 62% to 81%.

In cylindrical batteries having 1865 and 2170 form factors, the radius of the electrode assembly is about 9 mm to 10 mm. Therefore, the radial length of the segment section (f) cannot be secured at the level of 13 mm to 16 mm as in the embodiment, and the length of the segment-free section (c, circle 1) cannot be secured at the level of 4 mm to 7 mm, while the length of the uniform stacking number section (e) where the number of segment stacks is 10 or more cannot be secured at the level of 5 mm to 11 mm. This is because, in a conventional cylindrical battery, if the core radius is designed to be 2 mm as in the embodiment, the radius section in which the segment can be arranged is substantially only 7 mm to 8 mm. In addition, in a conventional cylindrical battery, the length of the electrode in the winding direction is about 600 mm to 980 mm. Such a short electrode length is only about 15% to 24% of the electrode length in the embodiment (positive electrode 3948 mm, negative electrode 4045 mm). Therefore, the numerical ranges for parameters h, i, and j cannot be easily derived from the design specifications of conventional cylindrical batteries.

Next, when the minimum height _h1 and maximum height _hN of the segment are the same in the segment height variable section (circle 2), a specific example will be given to explain how the number of layers of the segment changes along the radial direction of the folded surface area F depending on the diameter of the core C of the electrode assembly.

The electrode assemblies of Examples 6-1 to 6-6 have a radius of 22 mm, and the radius of the core C is 4 mm. The minimum height _h1 of the segment in the height variable section (circle 2) of the segment 61 is the same as 3 mm, and the maximum height _hN of the segment is changed in 1 mm increments from 5 mm to 10 mm. Therefore, in the electrode assemblies of Examples 6-1 to 6-6, the widths of the height variable section (circle 2) of the segment are 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, and 7 mm, respectively, and the segment-omitted section (circle 1) is a radius section from 4 mm to 7 mm.

The electrode assemblies of Examples 7-1 to 7-6 have a radius of 22 mm, and the radius of the core C is 2 mm. The minimum height _h1 of the segment in the height variable section (circle 2) of the segment 61 is the same as 3 mm, and the maximum height _hN of the segment is changed in 1 mm increments from 5 mm to 10 mm. Therefore, in the electrode assemblies of Examples 7-1 to 7-6, the widths of the height variable section (circle 2) of the segment are 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, and 7 mm, respectively, and the segment-free section (circle 1) is all the same as the radius section from 2 mm to 5 mm.

Figure 10e is a graph showing the results of counting the number of stacked pieces measured along the radial direction in the folded surface region F of the positive electrode formed on the upper part of the electrode assembly according to Examples 6-1 to 6-6 and Examples 7-1 to 7-6. Substantially the same results were observed in the folded surface region of the negative electrode.

In FIG. 10e, graph (a) shows the results of counting the number of laminated pieces measured along the radial direction in the folded surface region F for Examples 6-1 to 6-6, and graph (b) shows the results of counting the number of laminated pieces measured along the radial direction in the folded surface region F for Examples 7-1 to 7-6.

Referring to Fig. 10e, a uniform number of layers section b1 of the sub-segment appears in common to all examples. The uniform number of layers section b1 is a radial section of a flat region in the graph. The radial length of the uniform number of layers section b1 increases as the maximum height _hN of the sub-segment decreases when the minimum height _h1 of the sub-segment is the same. Meanwhile, in the uniform number of layers section b1, the number of layers of the sub-segment increases as the maximum height _hN of the sub-segment increases. In the examples, a reduced number of layers section b2 is identified adjacent to the uniform number of layers section b1.

In the embodiment, the number of layers of the segment in the uniform layer number section b1 is 10 or more. Preferably, the area where the number of layers of the segment is 10 or more can be set as a preferred welding target area.

In the examples, the uniform number of layers section b1 begins at the radius where the variable height section (circle 2) of the segment begins. In the cases of Examples 6-1 to 6-6, the radius where the variable height section (circle 2) of the segment begins is 7 mm, and in the cases of Examples 7-1 to 7-6, the radius where the variable height section (circle 2) of the segment begins is 5 mm.

Table 6 below shows the calculation results of various parameters for Examples 6-1 to 6-6 and Examples 7-1 to 7-6, including the ratio (e/f) of the length of the uniform stacking number section to the length from the radius point (7 mm, 5 mm) where the uniform stacking number section begins to the outermost point (22 mm) of the electrode assembly, and the ratio (d/f) of the length of the variable height section (circle 2) of the segment to the length from the radius point (7 mm, 5 mm) where the uniform stacking number section begins to the outermost point (22 mm) of the electrode assembly.

Referring to FIG. 10a and Table 6, Examples 6-6 and 7-6, the minimum height _h1 and maximum height _hN of the segment in the height variable section (circle 2) of the segment are the same, being 3 mm and 10 mm, respectively. However, Example 6-6 has a larger core radius by 2 mm than Example 7-6. Therefore, Example 6-6 has a uniform number of layers section (e) and a segment section (f) that are smaller by 2 mm than Example 7-6, and the number of layers of the segment in the uniform number of layers section is the same. This result is due to the difference in the core radius. From the results shown in Table 6, it can be seen that when the width of the height variable section (circle 2) of the segment is the same, the smaller the core radius (a), the smaller the ratio (d/f) of the height variable section (circle 2) decreases, while the ratio (e/f) of the uniform number of layers section increases. Referring to Table 6, it can be seen that the number of laminations of the segment is 13 to 26, the ratio (d/f) of the height variable section (circle 2) of the segment is 12% to 47%, and the ratio (e/f) of the length of the uniform number of laminations section is 40% to 76%. In addition, the ratio (c/(circle 1)) of the segment-omitted section to the radius (b-a) of the electrode assembly excluding the core is 15% to 17%. In addition, the ratio of the length of the electrode region corresponding to the segment-omitted section (circle 1) to the entire length of the electrode is 6%, the ratio of the length of the electrode region corresponding to the height variable section (circle 2) to the entire length of the electrode is 7% to 32%, and the ratio of the length of the electrode region corresponding to the uniform height section (circle 3) to the entire length of the electrode is 59% to 83%.

Cylindrical batteries having 1865 and 2170 form factors have an electrode assembly radius of about 9 mm to 10 mm. Therefore, the radial length of the segment section (f) cannot be secured to the level of 15 mm to 17 mm as in the embodiment, and the length of the segment-free section (circle 1) cannot be secured to about 3 mm while the length of the uniform stacking number section (e) where the number of stacked segments is 10 or more cannot be secured to the level of 6 mm to 13 mm. This is because, in a conventional cylindrical battery, when the core radius is designed to be 2 mm to 4 mm as in the embodiment, the radius section in which the segment can be arranged is substantially only 5 mm to 8 mm. In addition, in a conventional cylindrical battery, the length of the electrode in the winding direction is at the level of 600 mm to 980 mm. Such a short electrode length is only about 15% to 24% of the electrode length in the embodiment (positive electrode 3948 mm, negative electrode 4045 mm). Therefore, the numerical ranges for the parameters h, i, and j cannot be easily derived from the design specifications of the conventional cylindrical battery.

Considering the data in Tables 4 to 6 comprehensively, the number of layers of the segment in the uniform layer number section of the segment may be 11 to 26. The ratio (d/f) of the variable height section of the segment (circle 2) may be 6% to 47%. The ratio (e/f) of the uniform layer number section may be 31% to 82%. The ratio (c/(b-a)) of the length of the segment-omitted section (circle 1) to the radius of the electrode assembly excluding the core may be 15% to 35%. The ratio of the length of the electrode region corresponding to the segment-omitted section (circle 1) to the entire length of the electrode (length in the winding direction) may be 6% to 20%. The ratio of the length of the electrode region corresponding to the variable height section of the segment (circle 2) to the entire length of the electrode may be 3% to 32%. The ratio of the length of the electrode region corresponding to the uniform height section of the segment (circle 3) to the entire length of the electrode may be 59% to 87%.

Meanwhile, the parameters described in Tables 4 to 6 may vary depending on design factors including the radius of the core (a); the radius of the electrode assembly (b); the minimum height _h1 and maximum height _hN in the height variable section of the segment (circle 2); the amount of change in the height of the segment Δh per 1 mm increase in radius; and the thicknesses of the positive electrode, negative electrode, and separator.

Therefore, the number of laminations of the segment in the uniform lamination number section of the segment may be expanded to 10 to 35. The ratio (d/f) of the variable height section (circle 2) of the segment may be expanded to 1% to 50%. Also, the ratio (e/f) of the uniform lamination number section may be expanded to 30% to 85%. Also, the ratio (c/(b-a)) of the length of the segment-omitted section (circle 1) to the radius of the electrode assembly excluding the core may be expanded to 10% to 40%. Also, the ratio of the length of the electrode region corresponding to the segment-omitted section (circle 1) to the entire length of the electrode (length in the winding direction) may be expanded to 1% to 30%. Also, the ratio of the length of the electrode region corresponding to the variable height section (circle 2) of the segment to the entire length of the electrode may be expanded to 1% to 40%. Also, the ratio of the length of the electrode region corresponding to the uniform height section (circle 3) of the segment to the entire length of the electrode may be expanded to 50% to 90%. In the above-described embodiment, the height index N of the maximum height _hN of the sub-segment included in the height variable section (circle 2) and the height uniform section (circle 3) is 2 to 8. For example, referring to Table 4, the height index N for Example 1-1 and Example 1-7 is 2 and 8, respectively. However, the height index N may vary depending on the height change amount Δh of the sub-segment in the radial direction of the electrode assembly. When the radial length of the height variable section (circle 2) is fixed, if the height change amount Δh of the sub-segment decreases, the height index N increases accordingly, and vice versa is also possible. Preferably, the height index N is 2 to 20, and optionally can be further extended to 2 to 30.

In the folded surface regions F formed on the upper and lower parts of the electrode assembly, the uniform lamination number sections can be used as welding target regions for the current collector.

Preferably, the welded area of the current collector overlaps with the uniform lamination number section in the radial direction of the electrode assembly by at least 50%, and the higher the overlap ratio, the more preferable.

Preferably, other areas of the welding area of the current collector that do not overlap with the uniform lamination number section may overlap with the reduced lamination number section adjacent to the uniform lamination number section in the radial direction.

More preferably, other areas of the welded region of the current collector that do not overlap with the uniform lamination number section may overlap with areas of the reduced lamination number section where the overlap number of the divided segments is 10 or more.

Welding the current collector to an area where the number of laminated segments is 10 or more is preferable in terms of welding strength and in terms of preventing damage to the separation membrane and active material layer during welding. This is particularly useful when welding the current collector using a high-power laser with high transmission characteristics.

When a uniform-layer-count section, which has 10 or more stacked pieces, is welded to a current collector with a laser, even if the laser output is increased to improve welding quality, the uniform-layer-count section absorbs most of the laser energy to form a weld bead, preventing the separation membrane and active material layer below the folded surface region F from being damaged by the laser.

In addition, because the area irradiated with the laser has 10 or more stacked pieces, the weld beads are formed with sufficient volume and thickness. This ensures sufficient weld strength, and the resistance of the weld interface can be reduced to a level suitable for rapid charging.

The output of the laser when welding the current collector can be determined by the desired weld strength between the folded surface region F and the current collector. The weld strength increases in proportion to the number of stacked segments. This is because the greater the number of stacked segments, the greater the volume of the weld bead formed by the laser. The weld bead is formed as the material of the current collector and the material of the split segment are melted together. Therefore, a larger volume of the weld bead provides a stronger bond between the current collector and the folded surface region, resulting in lower contact resistance at the weld interface.

Preferably, the welding strength may be 2 kgf/cm2 or ^more , more preferably 4 kgf/ ^cm2 or more. The maximum welding strength may vary depending on the output of the laser welding device. As an example, the welding strength may be set to preferably 8 kgf/cm2 or ^less , more preferably 6 kgf/ ^cm2 or less. However, the present invention is not limited thereto.

When the weld strength satisfies the above numerical range, the physical properties of the weld interface do not deteriorate even when the electrode assembly is subjected to intense vibrations along the winding axis and/or radial directions, and the volume of the weld beads is sufficient to reduce the resistance of the weld interface.

The laser output required to meet the welding strength requirements varies depending on the laser device, but can be appropriately adjusted within the range of 250W to 320W or 40% to 100% of the maximum laser output specification provided by the device.

The weld strength may be defined as the tensile force (kgf/ ^cm2 ) per unit area of the current collector when the current collector begins to separate from the folded surface region F. Specifically, after welding of the current collector is completed, a tensile force is applied to the current collector and the magnitude of the force is gradually increased. When the tensile force exceeds a critical value, the pieces begin to separate from the weld interface. At this time, the tensile force applied to the current collector divided by the area of the current collector corresponds to the weld strength.

The folded surface area F is made up of multiple layers of laminated segments, and according to the embodiment described above, the number of laminated segments can be increased from a minimum of 10 to a maximum of 35.

The thickness of the positive electrode current collector (foil) constituting the uncoated portion 43 may be 10 μm to 25 μm, and the thickness of the negative electrode current collector (foil) constituting the uncoated portion 43 may be 5 μm to 20 μm. Therefore, the folded surface region F of the positive electrode may include an area where the total laminate thickness of the divided pieces is 100 μm to 875 μm. Also, the folded surface region F of the negative electrode may include an area where the total laminate thickness of the divided pieces is 50 μm to 700 μm.

Figure 10f is a top view of an electrode assembly showing a uniform lamination number section b1 and a reduced lamination number section b2 in the folded surface region F of the divided segments 61, 61' according to an embodiment of the present invention.

Referring to FIG. 10f, the area between the two circles shown by the thick solid lines corresponds to the folded surface area F of the segment, the area between the two circles shown by the dashed dotted lines corresponds to the uniform layer count area b1 where the number of layers of the segment is 10 or more, and the area outside the uniform layer count area b1 corresponds to the reduced layer count area b2.

For example, when the current collector _Pc is welded to the bent surface region F, a welding pattern _Wp is generated on the surface of the current collector _Pc . The welding pattern _Wp may be an array of line patterns or dot patterns. The welding pattern _Wp corresponds to the welding region and may overlap with the uniform layer number section b1 of the divided segment by 50% or more along the radial direction. Thus, a part of the welding pattern _Wp may be included in the uniform layer number section b1, and the remaining welding pattern _Wp may be included in the reduced layer number section b2 outside the uniform layer number section b1. Of course, in order to maximize the welding strength and reduce the resistance of the welding region, the entire welding pattern _Wp may overlap with the uniform layer number section b1.

The area of the folded surface region F may be defined as the sum of the area of the uniform lamination number section b1 and the area of the reduced lamination number section b2 of the divided segment. Since the ratio (e/f) of the uniform lamination number section b1 is 30% to 85%, preferably 31% to 82%, the ratio of the area of the uniform lamination number section b1 to the area of the folded surface region F may be 9% (30 ² /100 ² ) to 72% (85 ² /100 ² ), preferably 10% (31 ² /100 ² ) to 67% (82 ² /100 ² ).

Preferably, the end of the portion where the current collector _Pc contacts the folded surface region F may cover the end of the divided pieces 61, 61' folded toward the core C in the last winding turn of the uniform height section (circle 3). In this case, the welding pattern _Wp is formed in a state where the divided pieces 61, 61' are pressed by the current collector _Pc , so that the current collector _Pc and the folded surface region F are strongly bonded. As a result, the divided pieces 61, 61' stacked in the winding axis direction are tightly adhered to each other, so that the resistance at the welded interface is also low, and the phenomenon of the divided pieces 61, 61' lifting up can be prevented.

On the other hand, the bending direction of the split pieces may be opposite to the above-mentioned direction. That is, the split pieces may be bent from the core side to the outer periphery. In this case, the pattern in which the height of the split pieces changes along the winding direction (X-axis direction) may be opposite to that of the above-mentioned embodiment (variant form). For example, the height of the split pieces may be gradually decreased from the core to the outer periphery. In addition, the structure applied to the first part B1 and the structure applied to the second part B3 may be interchangeable. Preferably, the height of the split pieces may be gradually decreased from the core side to the outer periphery, and the split piece height change pattern may be designed so that when the split piece closest to the outer periphery of the electrode assembly is bent toward the outer periphery, the end of the split piece does not protrude outside the outer periphery of the electrode assembly.

The electrode structure of the above-described embodiment (variant) may be applied to at least one of the first electrode and the second electrode having different polarities included in a jelly roll type or other type of electrode assembly known in the art. Furthermore, when the electrode structure of the embodiment (variant) is applied to one of the first electrode and the second electrode, a conventional electrode structure may be applied to the other. Furthermore, the electrode structures applied to the first electrode and the second electrode may not be the same, but may be different.

As an example, when the first electrode and the second electrode are positive and negative electrodes, respectively, any one of the embodiments (variations) may be applied to the first electrode, and a conventional electrode structure (see FIG. 1) may be applied to the second electrode.

As another example, when the first electrode and the second electrode are a positive electrode and a negative electrode, respectively, any one of the embodiments (variations) may be selectively applied to the first electrode, and any one of the embodiments (variations) may be selectively applied to the second electrode.

In one embodiment of the present invention, the positive electrode active material coated on the positive electrode and the negative electrode active material coated on the negative electrode can be any active material known in the art without any restrictions.

As an example, the positive electrode active material may include an alkali metal compound represented by the general chemical formula A[A _x M _y ]O _2+z , where A includes at least one element of Li, Na, and K; M includes at least one element selected from Ni, Co, Mn, Ca, Mg, Al, Ti, Si, Fe, Mo, V, Zr, Zn, Cu, Al, Mo, Sc, Zr, Ru, and Cr; x≧0, 1≦x+y≦2, −0.1≦z≦2; and the stoichiometric coefficients x, y, and z are selected to maintain electrical neutrality of the compound.

As another example, the positive electrode active material may be an alkali metal compound xLiM ¹ O ₂ -(1-x)Li ₂ M ² O ₃ (wherein M ¹ includes at least one element having an average oxidation state of 3; M ² includes at least one element having an average oxidation state of 4; 0≦x≦1) as disclosed in U.S. Pat. Nos. 6,677,082 and 6,680,143, among others.

As yet another example, the positive electrode active material may have the general formula Li _a M ¹ _x Fe _1-x M ² _y P _1-y M ³ _z O _4-z (wherein M ¹ includes at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mg, and Al; M ² includes at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mg, Al, As, Sb, Si, Ge, V, and S; M ³ includes a halogen group element, optionally including F; 0<a≦2, 0≦x≦1, 0≦y<1, 0≦z<1; the stoichiometric coefficients a, x, y, and z are selected to maintain the compound's electrical neutrality), or Li ₃ M ₂ (PO ₄ ) ₃ [M includes at least one element selected from Ti, Si, Mn, Fe, Co, V, Cr, Mo, Ni, Al, Mg, and Al].

As yet another example, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; lithium manganese oxides such as those having the formula Li _1+x Mn _2-x O ₄ (x=0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , and LiMnO ₂ ; lithium copper oxide (Li ₂ CuO ₂ ); vanadium oxides such as LiV ₃ O ₅ , LiV ₃ O ₄ , V ₂ O ₅ , _and Cu ₂ V _{2 O 7 ;} The lithium intercalation material may be _a main component, such as nickel site type lithium nickel oxide represented by the chemical formula _{LiMn2- xMxO2} (M=Co, Ni, Fe, Cr, Zn or Ta, x=0.01-0.3); lithium manganese composite oxide represented by the chemical formula _{LiMn2- xMxO2} (M=Co, Ni, Fe, Cr, Zn or Ta, x=0.01-0.1) or _Li2Mn3MO8 (M=Fe, Co, Ni, Cu or Zn ₎ ; _LiMn2O4 in which part of the lithium is replaced by an alkaline earth metal ion; disulfide compound; _Fe2 ( _MoO4 ) ₃ or a composite oxide formed by a combination thereof.

The positive electrode current collector has a thickness of, for example, 3 μm to 500 μm. Such a positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector may have fine irregularities on its surface to increase the adhesive strength of the positive electrode active material, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

A conductive material may be further mixed into the positive electrode active material particles. Such a conductive material may be added in an amount of, for example, 1 to 50% by weight based on the total weight of the mixture including the positive electrode active material. Such a conductive material is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity. For example, graphite such as natural graphite and artificial graphite; carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

Preferably, the positive electrode active material may contain primary particles and/or secondary particles formed by agglomeration of primary particles.

The negative electrode is fabricated by applying and drying negative active material particles onto a negative current collector, and may further contain components such as the conductive material, binder, and solvent described above, as necessary.

The negative electrode current collector has a thickness of, for example, 3 μm to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, baked carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. may be used. In addition, like the positive electrode current collector, fine irregularities may be formed on the surface to strengthen the binding force of the negative electrode active material, and it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

For example, the negative electrode active material may be a carbon material, lithium metal or a lithium metal compound, silicon or a silicon compound, tin or a tin compound, etc. Metal oxides such as _TiO2 and _SnO2 having a potential of less than 2 V may also be used as the negative electrode active material. The carbon material may be either low crystalline carbon or high crystalline carbon.

As another example, the negative electrode active material may be carbon, such as non-graphitizable carbon or graphite-based carbon; metal composite oxides such as Li _x Fe ₂ O ₃ (0≦x≦1), Li _x WO ₂ (0≦x≦1), and Sn _x Me _1-x Me' _y O _z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of Groups 1, 2, and 3 of the periodic table, halogens; 0<x≦1;1≦y≦3;1≦z≦8); lithium metal; lithium alloys; silicon-based alloys; tin-based alloys; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, and GeO. _{For example} , oxides such as _Bi2O3 , _Bi2O4 , and _Bi2O5 ; conductive polymers such as polyacetylene; Li- _Co -Ni based materials _, and _the like can be used.

The binder polymer usable for the electrode is a component that assists in bonding between the electrode active material particles and the conductive material, etc., and to the electrode current collector, and is added, for example, at 1 to 50% by weight based on the total weight of the mixture containing the electrode active material. As such a binder polymer, any one binder polymer selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene vinyl acetate copolymer, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, and carboxymethyl cellulose, or a mixture of two or more of these may be used, but is not limited thereto.

Non-limiting examples of solvents used in the manufacture of electrodes include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water, or mixtures thereof. Such solvents provide the proper level of viscosity to form a desired level of slurry coating layer on the surface of the electrode current collector.

The negative electrode comprises a current collector and a negative electrode active material layer located on at least one surface of the current collector and containing a negative electrode active material, a binder polymer, and a conductive material, the negative electrode active material layer being composed of a lower layer region that is in surface contact with the current collector, and an upper layer region that is in surface contact with the lower layer region and extends to the surface of the negative electrode active material layer, and the lower layer region and the upper layer region may each independently contain at least one of graphite and a silicon-based compound as the negative electrode active material.

The lower layer region may contain natural graphite as the negative electrode active material, and the upper layer region may contain artificial graphite as the negative electrode active material.

The lower layer region and the upper layer region may each independently further contain a silicon-based compound as a negative electrode active material.

The silicon-based compound may include one or more of SiOx (0≦x≦2) and SiC.

According to one embodiment of the present invention, the negative electrode can be manufactured by applying a lower layer slurry containing a lower layer negative electrode active material to a current collector and drying it to form a lower layer region, and then applying an upper layer slurry containing an upper layer negative electrode active material on the lower layer region and drying it to form an upper layer region.

Alternatively, according to an embodiment of the present invention, the negative electrode may include a step of preparing a lower layer slurry including a lower layer negative electrode active material and an upper layer slurry including an upper layer negative electrode active material;
coating one surface of a negative electrode current collector with the lower layer slurry, and simultaneously or after a predetermined time lag, coating the upper layer slurry on the lower layer slurry;
and drying the coated underlayer slurry and overlayer slurry simultaneously to form an active material layer.

When the latter method is used, a mixed region (intermixing) in which different types of active materials are mixed may exist at the contact area between the lower and upper layers in the negative electrode. This is because when the active material layer is formed by simultaneously or continuously coating the lower layer slurry containing the lower layer negative electrode active material and the upper layer slurry containing the upper layer negative electrode active material on the current collector and then drying them simultaneously, a certain mixed area is generated at the interface where the lower layer slurry and the upper layer slurry contact before drying, and then this mixed area is formed in the form of a layer of the mixed area while being dried.

In one embodiment of the negative electrode active material layer of the present invention, the weight ratio (or the ratio of loading amount per unit area) of the upper layer region to the lower layer region may be 20:80 to 50:50, more specifically, 25:75 to 50:50.

The thicknesses of the lower and upper regions of the negative electrode active material layer according to one embodiment of the present invention may not be completely the same as the thicknesses of the coated lower layer slurry and the coated upper layer slurry. However, the thickness ratio of the lower and upper regions of the negative electrode active material layer according to one embodiment of the present invention finally obtained as a result of the drying or selective rolling process may be the same as the thickness ratio of the coated lower layer slurry and the coated upper layer slurry.

According to one embodiment of the present invention, a first slurry (slurry for a lower layer) is coated, and a second slurry (slurry for an upper layer) is coated on the first slurry at the same time or after a predetermined time difference, and the predetermined time difference may be 0.6 seconds or less, 0.02 seconds to 0.6 seconds, 0.02 seconds to 0.06 seconds, or 0.02 seconds to 0.03 seconds. Since the time difference when coating the first slurry and the second slurry occurs due to the coating device, it is more preferable that the first slurry and the second slurry are coated simultaneously. The second slurry may be coated on the first slurry using a device such as a double slot die.

The step of forming the active material layer may further include a step of rolling the active material layer after the drying step. In this case, the rolling may be performed by a method commonly used in the art, such as a roll press, and may be performed at a pressure of 1 to 20 MPa and a temperature of 15 to 30°C, for example.

The step of simultaneously drying the coated lower layer slurry and upper layer slurry to form an active material layer can be performed by a method commonly used in the art using a device that combines a hot air dryer and an infrared dryer.

The weight percentage of the first binder polymer in the solid content of the lower layer slurry may be the same as or greater than the weight percentage of the second binder polymer in the solid content of the upper layer slurry. According to one embodiment of the present invention, the weight percentage of the first binder polymer in the solid content of the lower layer slurry may be 1.0 to 4.2 times, 1.5 to 3.6 times, or 1.5 to 3 times the weight percentage of the second binder polymer in the solid content of the upper layer slurry.

When the ratio of the weight percentage of the first binder in the coated lower layer slurry to the weight percentage of the second binder in the coated upper layer slurry satisfies this range, the binder in the lower layer region does not become too small, so detachment of the electrode layer does not occur, and the binder in the upper layer region does not become too large, so the resistance of the upper layer of the electrode decreases, which is advantageous for rapid charging performance.

The weight percentage of the first binder polymer in the solid content of the lower layer slurry may be 2 to 30 weight percent, or 5 to 20 weight percent, and the weight percentage of the second binder polymer in the solid content of the upper layer slurry may be 0.5 to 20 weight percent, 1 to 15 weight percent, 1 to 10 weight percent, or 2 to 5 weight percent.

The total ratio (wt%) of the first binder polymer and the second binder polymer to the total solid content of the lower layer slurry and the upper layer slurry may be 2 to 20 wt%, or 5 to 15 wt%.

The separation membrane has a porous polymer substrate and porous coating layers that are located on both sides of the porous polymer substrate and contain inorganic particles and a binder polymer.

The porous polymer substrate may be a polyolefin-based porous substrate.

The polyolefin-based porous substrate may be in the form of a film or non-woven web. This porous structure facilitates the movement of electrolyte between the positive and negative electrodes, and increases the electrolyte impregnation of the substrate itself, ensuring excellent ion conductivity. It also prevents an increase in resistance inside the electrochemical device, preventing a decrease in the performance of the electrochemical device.

The polyolefin-based porous substrate used in the present invention can be any planar porous substrate typically used in electrochemical elements, and the material and shape can be selected from a variety of options depending on the purpose.

The polyolefin-based porous substrate may be, but is not limited to, a film or nonwoven web formed of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra-high molecular weight polyethylene, polypropylene, or a mixture of two or more of these.

The polyolefin-based porous substrate may have a thickness of 8 to 30 μm, but this is merely an example, and thicknesses outside the above range may be adopted in consideration of mechanical properties and the high-rate charge/discharge characteristics of the battery.

The nonwoven fabric sheet according to one embodiment of the present invention may be made of polyethylene (PE), polypropylene (PP), or a mixture thereof. For example, the nonwoven fabric sheet may be manufactured by fiber spinning. For example, the nonwoven fabric sheet may be manufactured by blending and spinning material fibers into fiber yarns at or above their melting points using a melt blown method.

The nonwoven fabric sheet may have an elongation ratio of 200 to 400%, more preferably 300 to 400%. If the elongation ratio is less than 200%, the possibility of electrodes coming into contact with each other when the nail penetrates increases, and if it exceeds 400%, the surrounding area also elongates when the nail penetrates, making the separation membrane thinner and reducing the barrier properties (blocking properties).

The nonwoven fabric sheet has a large number of pores with an average diameter of 0.1 to 10 μm. If the pore size is smaller than 0.1 μm, lithium ions and/or electrolytes cannot move smoothly, and if the pore size is larger than 10 μm, the effect of one embodiment of the present invention, which aims to prevent contact between the positive and negative electrodes, may not be achieved due to the stretching of the nonwoven fabric sheet when a nail penetrates it.

The nonwoven fabric sheet may have a porosity of 40 to 70%. If the porosity is less than 40%, lithium ions and/or electrolytes may not move smoothly, and if the porosity is greater than 70%, the effect of one embodiment of the present invention, which aims to prevent contact between the positive and negative electrodes due to the stretching of the nonwoven fabric sheet when a nail penetrates, may not be achieved. The nonwoven fabric sheet manufactured in this manner may have an air permeability of 1 to 20 seconds/100 mL.

The nonwoven fabric sheet may have a thickness of 10 to 20 μm, but this is merely an example and is not limited to this. Nonwoven fabric sheets with thicknesses outside the above range may also be used depending on the permeability of the nonwoven fabric sheet.

The nonwoven fabric sheet can be bonded to the separation membrane component below the nonwoven fabric sheet by lamination. Lamination can be performed at a temperature range of 100-150°C, but if lamination is performed at a temperature lower than 100°C, the lamination effect will not be achieved, and if lamination is performed at a temperature higher than 150°C, there is a risk of part of the nonwoven fabric melting.

The separation membrane according to one embodiment of the present invention bonded by lamination under the above conditions has improved resistance to nail penetration compared to a separation membrane made of a conventional nonwoven sheet, and compared to a separation membrane in which a layer containing inorganic particles is formed on at least one surface of a film or nonwoven sheet.

In the porous coating layer, the inorganic particles are packed together and in contact with each other, and are bound by the binder polymer, thereby forming interstitial volumes between the inorganic particles, and the interstitial volumes between the inorganic particles become empty spaces and can form pores.

The inorganic particles used in forming the porous coating layer may further include inorganic particles, i.e., inorganic particles that do not undergo oxidation and/or reduction reactions in the operating voltage range of an electrochemical device (e.g., 0 to 5 V based on Li/Li ⁺ ). In particular, when inorganic particles having ion-transfer ability are used, the ionic conductivity in the electrochemical device can be increased to improve performance. In addition, when inorganic particles having a high dielectric constant are used as the inorganic particles, the degree of dissociation of an electrolyte salt, e.g., a lithium salt, in a liquid electrolyte can be increased to improve the ionic conductivity of the electrolyte.

For the reasons described above, it is preferable that the inorganic particles include inorganic particles with a high dielectric constant having a dielectric constant of 5 or more, preferably 10 or more, inorganic particles having lithium ion transfer ability, or a mixture thereof.

Non-limiting examples of inorganic particles having a dielectric constant of 5 or greater include _BaTiO3 , Pb(Zr,Ti) _O3 (PZT), Pb1 _{-xLaxZr1- yTiyO3 (} PLZT), PB(Mg1 _{/3Nb2 /3 ) O3- PbTiO3 (} PMN-PT), hafnia ( _HfO2 ), _SrTiO3 , _SnO2 , _CeO2 , MgO, NiO, CaO, _ZnO , _ZrO2 , _Y2O3 , _Al2O3 , _TiO2 , _SiC , or mixtures thereof.

In particular, inorganic particles such as BaTiO ₃ , Pb(Zr,Ti)O ₃ (PZT), Pb _1-x La _x Zr _1-y Ti _y O ₃ (PLZT), PB(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ (PMN-PT) and hafnia (HfO ₂ ) not only exhibit high dielectric constant characteristics with a dielectric constant of 100 or more, but also have piezoelectricity in which charges are generated and a potential difference is generated between both sides when a certain pressure is applied and stretched or compressed, thereby preventing internal short circuiting between both electrodes due to external impact and improving the safety of the electrochemical device. In addition, when the inorganic particles having a high dielectric constant are mixed with inorganic particles having lithium ion transportability, the synergistic effect is doubled.

The inorganic particles having lithium ion transport ability are inorganic particles that contain lithium elements but do not store lithium but have the function of transporting lithium ions. The inorganic particles having lithium ion transport ability can transport and transport lithium ions through a type of defect present inside the particle structure, thereby improving the lithium ion conductivity in the battery and thereby improving the battery performance. Non-limiting examples of the inorganic particles having lithium ion transfer ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0<x<2, 0<y<3), lithium aluminum titanium phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0<x<2, 0<y<1, 0<z<3), (LiAlTiP) _x O _y -based glass (0<x<4, 0<y<13) such as 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ O ₅ , lithium lanthanum titanate (Li _x La _y TiO ₃ , 0<x<2, 0<y<3), Li _3.25 Ge _0.25 P _Examples of the _glass include lithium germanium thiophosphate (Li _x Ge _y P _z S _w , 0<x<4, 0<y<1, 0<z<1, 0<w<5) such as Li ₃ N, lithium nitride (Li _x N _y , 0<x<4, 0<y<2) such as Li ₃ PO ₄ -Li ₂ S-SiS ₂ , SiS _2- based glass (Li _x Si _y S _z , 0<x<3, 0<y<2, 0<z<4) such as LiI-Li ₂ S-P ₂ S _5, P ₂ S ₅ -based glass (Li _x P _y S _z , 0<x<3, 0<y<3, 0<z<7) and mixtures thereof.

There is no limit to the size of the inorganic particles in the porous coating layer, but it is preferably 0.001 to 10 μm in order to form a coating layer of uniform thickness and to have an appropriate porosity. If it is less than 0.001 μm, the dispersibility of the inorganic particles will decrease, and if it exceeds 10 μm, the thickness of the porous coating layer will increase, the mechanical properties will decrease, and the pore size will become excessively large, making it highly likely that an internal short circuit will occur during charging and discharging of the battery.

The binder polymer forming the porous coating layer may be any one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, and carboxymethyl cellulose, or a mixture of two or more of these, but is not limited thereto.

The composition ratio of inorganic particles and binder polymer used in the porous coating layer is preferably, for example, in the range of 50:50 to 99:1, and more preferably 70:30 to 95:5. If the content of inorganic particles relative to the binder polymer is less than 50 parts by weight, the content of binder polymer increases, and the improvement of the thermal safety of the separator may be reduced. In addition, the pore size and porosity may decrease due to the reduction in the vacant space formed between the inorganic particles, and the final battery performance may be reduced. If the content of inorganic particles exceeds 99 parts by weight, the content of binder polymer is too small, and the peel resistance of the porous coating layer may be weakened. The thickness of the porous coating layer is not particularly limited, but is preferably 0.01 to 20 μm. In addition, the pore size and porosity are also not particularly limited, but the pore size is preferably 0.001 to 10 μm, and the porosity is preferably 10 to 90%. The pore size and porosity mainly depend on the size of the inorganic particles, but for example, when inorganic particles with a particle size of 1 μm or less are used, the pores formed will also be approximately 1 μm or less. Such a pore structure will be filled with the electrolyte that is injected later, and the filled electrolyte will play a role in ion transmission. If the pore size and porosity are less than 0.001 μm and 10%, they will act as a resistance layer, and if they exceed 10 μm and 90%, the mechanical properties may deteriorate.

The porous coating layer can be formed by dissolving or dispersing a binder polymer in a dispersion medium, adding inorganic particles to obtain a slurry for forming a porous coating layer, and coating and drying the slurry on at least one surface of a substrate. The dispersion medium preferably has a solubility index similar to that of the binder polymer to be used and a low boiling point. This is to facilitate uniform mixing and subsequent removal of the dispersion medium. Non-limiting examples of dispersing media that can be used include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water, or mixtures thereof.

It is preferable to add inorganic particles to the dispersion liquid in which the binder polymer is dispersed in the dispersion medium, and then crush the inorganic particles. In this case, the crushing time is preferably 1 hour to 20 hours, and the size of the crushed inorganic particles is preferably 0.001 to 10 μm as described above. As the crushing method, a conventional method can be used, and in particular, the ball mill method is preferable.

Then, the binder polymer dispersion in which the inorganic particles are dispersed is coated on at least one surface of the porous polymer substrate under a humidity condition of 10 to 80% and dried. The method of coating the dispersion on the porous polymer substrate may be a conventional coating method well known in the art, and various methods such as dip coating, die coating, roll coating, comma coating, or a combination thereof may be applied.

In addition to the inorganic particles and binder polymer described above, the components of the porous coating layer may further include other additives such as conductive materials.

The final separator produced according to one embodiment of the present invention may have a thickness of 1-100 μm or 5-50 μm. If the thickness is less than 1 μm, the separator may not function adequately and mechanical properties may deteriorate, while if the thickness exceeds 100 μm, the battery properties may deteriorate during high-rate charging and discharging. In addition, the separator may have a porosity of 40-60% and an air permeability of 150-300 sec/100 mL.

According to one embodiment of the present invention, the porous polymer substrate may be made of polyethylene or polypropylene. In addition, the inorganic particles in the porous coating layer may be made of Al oxide or Si oxide coating materials.

When using a separator according to an embodiment of the present invention, a porous coating layer is provided on both sides of a porous polymer substrate, so that a uniform solid electrolyte interface layer can be formed due to improved electrolyte impregnation performance, and superior air permeability can be secured compared to conventional one-sided inorganic coating separators. For example, it can be within 120s/100cc. In addition, even if inorganic porous coating layers are provided on both sides, it is possible to achieve a thickness at the same level as conventional one-sided inorganic coating separators. For example, it can be within 15.0 μm.

In addition, when using a separator according to an embodiment of the present invention, the stability of the separator is improved, and heat resistance and compression resistance can be ensured. Specifically, heat resistance with thermal shrinkage of 5% or less at 180°C can be ensured, and puncture strength of 550 gf or more can be ensured. When core deformation occurs during cycling of a battery using such a separator, damage or penetration of the separator at the step of the core can be prevented.

As the separation membrane, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, an ethylene/methacrylate copolymer, etc., can be used alone or in a laminate of these. As another example, the separation membrane can be made of a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting point glass fiber, polyethylene terephthalate fiber, etc.

The structure of an electrode assembly according to one embodiment of the present invention is described in detail below.

Figure 11 is a cross-sectional view of a jelly-roll type electrode assembly 80 in which the electrode 40 of the first embodiment is applied to the first electrode (positive electrode) and the second electrode (negative electrode) along the Y-axis direction (winding axis direction).

The electrode assembly 80 can be manufactured by the winding method described with reference to FIG. 2. For ease of explanation, the protruding structures of the first uncoated portion 43a and the second uncoated portion 43b extending outside the separation membrane are shown in detail, and the winding structures of the first electrode, the second electrode, and the separation membrane are not shown. The first uncoated portion 43a protruding upward extends from the first electrode, and the second uncoated portion 43b protruding downward extends from the second electrode.

The pattern in which the height of the first and second uncoated portions 43a and 43b varies is shown only diagrammatically. That is, the height of the uncoated portion may vary irregularly depending on the cutting position of the cross section. As an example, if the side of the trapezoidal segments 61, 61' or the cutting groove 63 is cut, the height of the uncoated portion in the cross section will be lower than the height H of the segments 61, 61'. Therefore, it should be understood that the height of the uncoated portion shown in the drawing showing the cross section of the electrode assembly corresponds to the average of the heights of the uncoated portions included in each winding turn (H in Figures 7b and 8b).

Referring to FIG. 11, the first uncoated portion 43a includes a first portion B1 adjacent to the core of the electrode assembly 80, a second portion B3 adjacent to the outer peripheral surface of the electrode assembly 80, and a third portion B2 interposed between the first portion B1 and the second portion B3.

The height of the second portion B3 (length in the Y-axis direction) is relatively lower than the height of the third portion B2. This prevents the beading portion of the battery housing from coming into contact with the second portion B3 as it is pressed against the second portion B3, which could cause an internal short circuit.

The second uncoated portion 43b has the same structure as the first uncoated portion 43a. In one modified embodiment, the second uncoated portion 43b may have a conventional electrode structure or an electrode structure of another embodiment (modified embodiment).

The ends 81 of the first uncoated portion 43a and the second uncoated portion 43b may be bent in the radial direction of the electrode assembly 80, for example, from the outer periphery side to the core side. In this case, the second portion B3 may not be substantially bent.

Figure 12 is a cross-sectional view of a jelly-roll type electrode assembly 90 in which the electrode 45 of the second embodiment is applied to the first electrode (positive electrode) and the second electrode (negative electrode) along the Y-axis direction (winding axis direction).

Referring to FIG. 12, the first uncoated portion 43a of the first electrode includes a first portion B1 adjacent to the core of the electrode assembly 90, a second portion B3 adjacent to the outer peripheral surface of the electrode assembly 90, and a third portion B2 interposed between the first portion B1 and the second portion B3.

The height of the second portion B3 is relatively lower than the height of the third portion B2, and decreases gradually or in steps from the core side toward the outer periphery. This prevents the beading portion of the battery housing from coming into contact with the second portion B3 as it is pressed against the second portion B3, which could cause an internal short circuit.

The second uncoated portion 43b has the same structure as the first uncoated portion 43a. In one modified embodiment, the second uncoated portion 43b may have a conventional electrode structure or an electrode structure of another embodiment (modified embodiment).

The ends 91 of the first uncoated portion 43a and the second uncoated portion 43b may be bent in the radial direction of the electrode assembly 90, for example, from the outer periphery side to the core side. In this case, the outermost portion 92 of the second portion B3 may not be substantially bent.

Figure 13 is a cross-sectional view of a jelly roll-type electrode assembly 100 in which any one of the electrodes 50, 60, and 70 of the third to fifth embodiments (variations thereof) is applied to the first electrode (positive electrode) and the second electrode (negative electrode) along the Y-axis direction (winding axis direction).

Referring to FIG. 13, the uncoated portion 43a of the first electrode includes a first portion B1 adjacent to the core of the electrode assembly 100, a second portion B3 adjacent to the outer peripheral surface of the electrode assembly 100, and a third portion B2 interposed between the first portion B1 and the second portion B3.

The height of the first portion B1 is relatively lower than the height of the third portion B2. In addition, the folding length of the innermost uncoated portion 43a in the third portion B2 is equal to or shorter than the radial length R of the first portion B1. The folding length H corresponds to the distance from the point where the uncoated portion 43a is folded to the upper end of the uncoated portion 43a. In a modified example, the folding length H may be smaller than the sum of the radial length R of the first portion B1 and 10% of the radius of the core 102.

Therefore, even if the third portion B2 is bent, 90% or more of the diameter of the core 102 of the electrode assembly 100 is open to the outside. The core 102 is a cavity in the center of the electrode assembly 100. If the core 102 is not blocked, the electrolyte injection process is not hindered, and the efficiency of the electrolyte injection is improved. In addition, a welding tool can be inserted through the core 102 to easily perform the welding process between the negative (or positive) side current collector and the battery housing (or terminal).

The height of the second portion B3 is relatively lower than the height of the third portion B2. This prevents the beading portion of the battery housing from coming into contact with the second portion B3 when the beading portion is pressed against the second portion B3, which can cause an internal short circuit.

In one modified embodiment, the height of the second portion B3 may decrease gradually or in steps, unlike that shown in FIG. 13. Also, in FIG. 13, the height of the third portion B2 is equal in a portion on the outer periphery, but the height of the third portion B2 may increase gradually or in steps from the boundary between the first portion B1 and the third portion B2 to the boundary between the third portion B2 and the second portion B3. When the third portion B2 is divided into a plurality of segments, the section where the height of the plain portion 43a changes corresponds to the height variable section of the segment (circle 2 in FIG. 10a).

The second uncoated portion 43b has the same structure as the first uncoated portion 43a. In one modified embodiment, the second uncoated portion 43b may have a conventional electrode structure or an electrode structure of another embodiment (modified embodiment).

The ends 101 of the first uncoated portion 43a and the second uncoated portion 43b may be bent in the radial direction of the electrode assembly 100, for example, from the outer periphery side to the core side. At this time, the first portion B1 and the second portion B3 are not substantially bent.

When the third portion B2 includes multiple segments, the bending stress is alleviated, and the uncoated portion 43a near the bending point can be prevented from being torn or abnormally deformed. In addition, when the width and/or height and/or spacing pitch of the segments are adjusted within the numerical range of the above-mentioned embodiment, the segments are folded toward the core and overlap each other to an extent that sufficient welding strength can be ensured, and no open space (gap) is formed in the folded surface area.

Figure 14 is a cross-sectional view of an electrode assembly 110 according to yet another embodiment of the present invention, cut along the Y-axis (winding axis) direction.

Referring to FIG. 14, the electrode assembly 110 has substantially the same configuration as the electrode assembly 100 of FIG. 13, except that the height of the second portion B3 is substantially the same as the outermost height of the third portion B2.

The second portion B3 may include multiple segments. The configuration of the multiple segments is substantially the same as that of the fourth and fifth embodiments (variant forms) of the electrode.

In the electrode assembly 110, the height of the first portion B1 is relatively lower than the height of the third portion B2. In addition, the bend length H of the uncoated portion located at the innermost side in the third portion B2 is equal to or shorter than the radial length R of the first portion B1. Preferably, the first portion B1 may be a segment-omitted section (circle 1 in FIG. 10a) that does not have a segment. In a modified example, the bend length H may be smaller than the sum of the radial length R of the first portion B1 and 10% of the radius of the core 112.

Therefore, even if the third portion B2 is bent, 90% or more of the diameter of the core 112 of the electrode assembly 110 is open to the outside. If the core 112 is not blocked, the electrolyte injection process is not hindered, and the efficiency of the electrolyte injection is improved. In addition, a welding tool can be inserted through the core 112 to easily perform the welding process between the negative (or positive) side current collector and the battery housing (or terminal).

In one modified embodiment, the structure in which the height of the third portion B2 increases gradually or in steps from the core side toward the outer periphery side can be extended to the second portion B3. In this case, the height of the uncoated portion 43a can increase gradually or in steps from the boundary between the first portion B1 and the third portion B2 to the outermost surface of the electrode assembly 110.

The second uncoated portion 43b has the same structure as the first uncoated portion 43a. In one modified embodiment, the second uncoated portion 43b may have a conventional electrode structure or an electrode structure of another embodiment (modified embodiment).

The ends 111 of the first uncoated portion 43a and the second uncoated portion 43b can be bent in the radial direction of the electrode assembly 110, for example, from the outer periphery side to the core side. At this time, the first portion B1 is not substantially bent.

When the third part B2 and the second part B3 include multiple segments, the bending stress is alleviated, and the uncoated portions 43a, 43b near the bending points can be prevented from being torn or abnormally deformed. In addition, when the width and/or height and/or spacing pitch of the segments are adjusted within the numerical range of the above-mentioned embodiment, the segments are folded toward the core and overlap each other to an extent that sufficient welding strength can be ensured, and no open space (gap) is formed in the folded surface area.

Figure 15 is a cross-sectional view of an electrode assembly 120 according to yet another embodiment of the present invention, cut along the Y-axis (winding axis) direction.

Referring to FIG. 15, the electrode assembly 120 differs from the electrode assembly 100 of FIG. 13 only in that the height of the third portion B2 has a pattern in which it gradually or stepwise increases and then decreases, and the other configurations are substantially the same. The radius section in which the height of the third portion B2 varies can be considered as a height variable section of the segment (circle 2 in FIG. 10a). In this case, too, the height variable section of the segment can be designed so that a uniform stack number section in which the number of stacked segments of 10 or more of the segment appears in the above-mentioned preferred numerical range in the folded surface region F formed while the third portion B2 is folded.

Such a change in the height of the third portion B2 can be achieved by adjusting the height of the staircase pattern (see FIG. 6) or the segment (see FIG. 7a or FIG. 8a) included in the third portion B2.

In the electrode assembly 120, the height of the first portion B1 is relatively lower than the height of the third portion B2. In addition, the bend length H of the uncoated portion located at the innermost side in the third portion B2 is equal to or shorter than the radial length R of the first portion B1. The section corresponding to the first portion B1 corresponds to the segment-omitted section (circle 1 in FIG. 10a) that does not have a segment. In a modified example, the bend length H may be smaller than the sum of the radial length R of the first portion B1 and 10% of the radius of the core 102.

Therefore, even if the third portion B2 is bent toward the core side, the core 122 of the electrode assembly 120 is open to the outside by more than 90% of its diameter. If the core 122 is not blocked, the electrolyte injection process is not hindered, and the efficiency of the electrolyte injection is improved. In addition, a welding tool can be inserted through the core 122 to easily perform the welding process between the negative (or positive) side current collector and the battery housing (or terminal).

The height of the second portion B3 is relatively lower than the height of the third portion B2, and preferably no dividing piece may be formed on the second portion B3. This can prevent the beading portion and the second portion B3 from coming into contact with each other and causing an internal short circuit when the beading portion of the battery housing is pressed against the second portion B3. In one modified example, the height of the second portion B3 may decrease gradually or in stages toward the outer periphery.

The second uncoated portion 43b has the same structure as the first uncoated portion 43a. In a modified embodiment, the second uncoated portion 43b may have a conventional electrode structure or an electrode structure of another embodiment (modified form).

The ends 121 of the first uncoated portion 43a and the second uncoated portion 43b may be bent from the outer periphery side of the electrode assembly 120 to the core side. At this time, the first portion B1 and the second portion B3 are not substantially bent.

When the third portion B2 includes multiple segments, the bending stress is alleviated, thereby preventing the uncoated portions 43a, 43b from being torn or abnormally deformed. In addition, when the width and/or height and/or spacing pitch of the segments are adjusted within the numerical range of the above-mentioned embodiment, the segments are folded toward the core and overlap each other to an extent that sufficient welding strength is ensured, and no open space (gap) is formed in the folded surface area.

Figure 16 is a cross-sectional view of an electrode assembly 130 according to yet another embodiment of the present invention, cut along the Y-axis (winding axis) direction.

Referring to FIG. 16, the electrode assembly 130 differs from the electrode assembly 120 of FIG. 15 in that the height of the second portion B3 decreases gradually or stepwise from the boundary between the second portion B3 and the third portion B2 toward the outermost surface of the electrode assembly 130, but the other configurations are substantially the same.

Such a change in the height of the second portion B3 can be achieved by extending the staircase pattern (see FIG. 6) included in the third portion B2 to the second portion B3 and gradually or stepwise decreasing the height of the pattern toward the outer periphery. In another variation, the change in the height of the second portion B3 can be achieved by extending the segment structure of the third portion B2 to the second portion B3 and gradually or stepwise decreasing the height of the segment toward the outer periphery.

In the electrode assembly 130, the height of the first portion B1 is relatively lower than the height of the third portion B2. In addition, the bend length H of the uncoated portion located at the innermost side in the third portion B2 is equal to or shorter than the radial length R of the first portion B1. The first portion B1 corresponds to a segment-free section (circle 1 in FIG. 10a) that does not have a segment. In a modified example, the bend length H may be smaller than the sum of the radial length R of the first portion B1 and 10% of the radius of the core 102.

Therefore, even if the third portion B2 is bent toward the core side, 90% or more of the diameter of the core 132 of the electrode assembly 130 is open to the outside. If the core 132 is not blocked, the electrolyte injection process is not hindered, and the efficiency of the electrolyte injection is improved. In addition, a welding tool can be inserted through the core 132 to easily perform the welding process between the negative (or positive) side current collector and the battery housing (or terminal).

The second uncoated portion 43b has the same structure as the first uncoated portion 43a. In one modified embodiment, the second uncoated portion 43b may have a conventional electrode structure or an electrode structure of another embodiment (modified embodiment).

The ends 131 of the first uncoated portion 43a and the second uncoated portion 43b may be bent from the outer periphery side of the electrode assembly 130 toward the core side. At this time, the first portion B1 is not substantially bent.

When the third part B2 and the second part B3 include multiple segments, the bending stress is alleviated, and the uncoated portions 43a, 43b near the bending points can be prevented from being torn or abnormally deformed. In addition, when the width and/or height and/or spacing pitch of the segments are adjusted within the numerical range of the above-mentioned embodiment, the segments are folded toward the core and overlap each other to an extent that sufficient welding strength can be ensured, and no open space (gap) is formed in the folded surface area.

Meanwhile, in the above-mentioned embodiment (variant), the ends of the first and second plain portions 43a and 43b may be folded from the core side to the outer periphery. In this case, it is preferable that the second portion B3 is designed as a section without a plain portion (circle 1 in FIG. 10a) without a plain portion and is not folded to the outer periphery. Also, the radial width of the second portion B3 may be the same as or greater than the length to which the outermost plain portion (or the plain portion) of the third portion B2 is folded. As a result, when the outermost plain portion (or the plain portion) of the third portion B2 is folded to the outer periphery, the end of the folded portion does not protrude beyond the outer periphery of the electrode assembly toward the inner surface of the battery housing. Also, the change pattern of the plain portion structure may be opposite to that of the above-mentioned embodiment (variant). For example, the height of the plain portion may increase stepwise or gradually from the core side to the outer periphery. That is, by arranging a segment-free section (circle 1 in FIG. 10a), a segment-height variable section (circle 2 in FIG. 10a), and a segment-height uniform section (circle 3 in FIG. 10a) in that order from the outer periphery side to the core side of the electrode assembly, a uniform-number-of-layers section with 10 or more segment-layers may appear in a preferred numerical range in the folded surface region.

The various electrode assembly structures according to embodiments of the present invention can be applied to cylindrical batteries.

Preferably, the cylindrical battery may be, for example, a cylindrical battery having a form factor ratio (defined as the diameter divided by the height of the cylindrical battery, i.e., the ratio of height (H) to diameter (Φ)) of greater than about 0.4. Here, form factor refers to a value that indicates the diameter and height of a cylindrical battery.

Preferably, the diameter of the cylindrical battery may be between 40mm and 50mm, and the height may be between 60mm and 130mm. The form factor of a cylindrical battery in one embodiment may be, for example, 46110, 4875, 48110, 4880, or 4680. In the form factor number, the first two digits indicate the diameter of the battery, and the remaining digits indicate the height of the battery.

When an electrode assembly having a tabless structure is applied to a cylindrical battery with a form factor ratio exceeding 0.4, the stress applied in the radial direction when bending the plain part is large, and the plain part is easily torn. Also, when welding a current collector to the bent surface area of the plain part, in order to ensure sufficient welding strength and reduce resistance, the number of layers of the plain part in the bent surface area must be sufficiently increased. These requirements can be achieved by the electrode and electrode assembly according to an embodiment (variant) of the present invention.

The battery according to one embodiment of the present invention may be a cylindrical battery having a generally cylindrical shape with a diameter of about 46 mm, a height of about 110 mm, and a form factor ratio of 0.418.

In another embodiment, the battery may be a generally cylindrical battery having a diameter of about 48 mm, a height of about 75 mm, and a form factor ratio of 0.640.

In yet another embodiment, the battery may be a generally cylindrical battery having a diameter of about 48 mm, a height of about 110 mm, and a form factor ratio of 0.436.

In yet another embodiment, the battery may be a generally cylindrical battery having a diameter of about 48 mm, a height of about 80 mm, and a form factor ratio of 0.600.

In yet another embodiment, the battery may be a generally cylindrical battery having a diameter of about 46 mm, a height of about 80 mm, and a form factor ratio of 0.575.

Conventionally, batteries with a form factor ratio of approximately 0.4 or less have been used. That is, conventionally, for example, 1865 batteries, 2170 batteries, etc. have been used. In the case of an 1865 battery, its diameter is approximately 18 mm, its height is approximately 65 mm, and its form factor ratio is 0.277. In the case of a 2170 battery, its diameter is approximately 21 mm, its height is approximately 70 mm, and its form factor ratio is 0.300.

The cylindrical battery according to one embodiment of the present invention is described in detail below.

Figure 17 is a cross-sectional view of a cylindrical battery 140 according to one embodiment of the present invention cut along the Y-axis direction.

Referring to FIG. 17, a cylindrical battery 140 according to one embodiment of the present invention includes an electrode assembly 141 including a first electrode, a separator, and a second electrode, a battery housing 142 that houses the electrode assembly 141, and a seal 143 that seals the open end of the battery housing 142.

The battery housing 142 is a cylindrical container with an opening at the top. The battery housing 142 is made of a conductive metal material such as aluminum, steel, or stainless steel. A nickel coating layer may be formed on the surface of the battery housing 142. The battery housing 142 accommodates the electrode assembly 141 in the inner space through the top opening, and also accommodates the electrolyte.

The electrolyte can be a salt of the structure A ⁺ B ⁻ , where A ⁺ includes ions of an alkali metal cation such as Li ⁺ , Na ⁺ , K ⁺ , or combinations thereof. And B ⁻ is F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , NO ₃ ⁻ , N(CN) ₂ ⁻ , BF ₄ ⁻ , ClO ₄ ⁻ , AlO ₄ ⁻ , AlCl ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , AsF ₆ ⁻ , BF ₂ C ₂ O ₄ ^- , BC ₄ O ₈ ^- , (CF ₃ ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , CF ₃ SO ₃ ^- , C ₄ F ₉ SO ₃ ⁻ , CF _The compound _contains one ^or _{more anions selected from the} group consisting _of ^CF3CF2SO3- _, (CF3SO2) ^{2N-, (FSO2)2N-} _{, CF3CF2} ⁽ _CF3 ⁾ _{2CO- ,} ⁽ _CF3SO2 ) ^2CH- _{, ( SF5 ) 3C-} , ( _CF3SO2 ^{) 3C-} , _CF3 ⁽ _{CF2 ) 7SO3-} ^, _CF3CO2- , _CH3CO2- , ^SCN- , and _{( CF3CF2SO2 ) 2N- .}

The electrolyte may also be used by dissolving it in an organic solvent. Examples of the organic solvent that may be used include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma-butyrolactone, and mixtures thereof.

The electrode assembly 141 may have a jelly-roll structure, but the present invention is not limited thereto. As shown in FIG. 2, the electrode assembly 141 may be manufactured by winding a laminate formed by stacking a lower separator, a first electrode, an upper separator, and a second electrode in sequence at least once, around a winding shaft C.

The first electrode and the second electrode have different polarities. That is, if one has a positive polarity, the other has a negative polarity. At least one of the first electrode and the second electrode may have an electrode structure according to the above-mentioned embodiment (variant form). Also, the other of the first electrode and the second electrode may have a conventional electrode structure or an electrode structure according to the embodiment (variant form). The number of electrode pairs included in the electrode assembly 141 is not limited to one, and may be two or more.

The first uncoated portion 146a of the first electrode and the second uncoated portion 146b of the second electrode protrude from the upper and lower portions of the electrode assembly 141, respectively. The first electrode has the electrode structure of the first embodiment (variant form). Therefore, the height of the second portion B3 of the first uncoated portion 146a is lower than the height of the uncoated portions of the other portions. The second portion B3 is spaced a predetermined distance from the inner circumferential surface of the battery housing 142, particularly the beading portion 147. Therefore, since the second portion B3 of the first electrode does not contact the battery housing 142 electrically connected to the second electrode, an internal short circuit of the cylindrical battery 140 is prevented.

The second uncoated portion 146b of the second electrode may have the same structure as the first uncoated portion 146a. In other variants, the second uncoated portion 146b may selectively have the structure of the uncoated portion of the electrode according to the embodiment (variant).

The sealing body 143 may include a cap 143a having a plate shape, a first gasket 143b having insulating properties and providing airtightness between the cap 143a and the battery housing 142, and a connecting plate 143c electrically and mechanically connected to the cap 143a.

The cap 143a is a part made of a conductive metal material and covers the upper opening of the battery housing 142. The cap 143a is electrically connected to the first uncoated portion 146a of the first electrode and is electrically insulated from the battery housing 142 through the first gasket 143b. Therefore, the cap 143a can function as the first electrode terminal (e.g., the positive electrode) of the cylindrical battery 140.

The cap 143a is placed on a beading portion 147 formed on the battery housing 142 and fixed by a crimping portion 148. A first gasket 143b may be interposed between the cap 143a and the crimping portion 148 to ensure airtightness of the battery housing 142 and to provide electrical insulation between the battery housing 142 and the cap 143a. The cap 143a may have a protrusion 143d formed to protrude upward from its center.

The battery housing 142 is electrically connected to the second uncoated portion 146b of the second electrode. Thus, the battery housing 142 has the same polarity as the second electrode. If the second electrode has a negative polarity, the battery housing 142 also has a negative polarity.

The battery housing 142 has a beading portion 147 and a crimping portion 148 at the upper end. The beading portion 147 is formed by pressing in around the outer periphery of the battery housing 142. The beading portion 147 prevents the electrode assembly 141 housed inside the battery housing 142 from slipping out of the upper end opening of the battery housing 142, and can function as a support portion on which the sealing body 143 is placed.

The inner circumferential surface of the beading portion 147 is spaced apart from the second portion B3 of the first electrode by a predetermined distance. More specifically, the lower end of the inner circumferential surface of the beading portion 147 is spaced apart from the second portion B3 of the first electrode by a predetermined distance. In addition, since the second portion B3 has a low height, it is not substantially affected when the battery housing 142 is pressed from the outside to form the beading portion 147. Therefore, the second portion B3 is not compressed by other components such as the beading portion 147, thereby preventing partial deformation of the electrode assembly 141 and preventing an internal short circuit of the cylindrical battery 140.

Preferably, if the pressing depth of the beading portion 147 is D1 and the radial length from the inner peripheral surface of the battery housing 142 to the boundary point between the second portion B3 and the third portion B2 is D2, the relational expression "D1≦D2" can be satisfied. In this case, when the battery housing 142 is pressed in to form the beading portion 147, damage to the second portion B3 is substantially prevented.

The crimping portion 148 is formed on the upper portion of the beading portion 147. The crimping portion 148 is extended and folded to enclose the outer circumferential surface of the cap 143a placed on the beading portion 147 and a part of the upper surface of the cap 143a.

The cylindrical battery 140 may further include a first current collector 144 and/or a second current collector 145 and/or an insulator 146.

The first current collector 144 is coupled to the top of the electrode assembly 141. The first current collector 144 is made of a conductive metal material such as aluminum, copper, steel, nickel, etc., and is electrically connected to the first uncoated portion 146a of the first electrode. The electrical connection may be made through welding. A lead 149 may be connected to the first current collector 144. The lead 149 may extend above the electrode assembly 141 and be coupled to the connection plate 143c, or may be directly coupled to the underside of the cap 143a. The lead 149 may be coupled to other components through welding.

Preferably, the first current collector 144 may be formed integrally with the lead 149. In this case, the lead 149 may have a long plate shape extending outward from near the center of the first current collector 144.

The first current collector 144 may have a plurality of projections and recesses (not shown) formed radially on its underside. If radial projections and recesses are provided, the first current collector 144 may be pressed against the projections to press the first uncoated portion 146a of the first electrode into the projections and recesses.

The first current collector 144 is connected to an end of the first uncoated portion 146a. The connection between the first uncoated portion 146a and the first current collector 144 may be performed, for example, by laser welding. Laser welding may be performed by partially melting the base material of the first current collector 144. In a modified example, the welding between the first current collector 144 and the first uncoated portion 146a may be performed with solder interposed. In this case, the solder may have a lower melting point than the first current collector 144 and the first uncoated portion 146a. Laser welding may be replaced by resistance welding, ultrasonic welding, spot welding, etc.

A second current collector 145 may be attached to the bottom surface of the electrode assembly 141. One side of the second current collector 145 may be attached to the second uncoated portion 146b by welding, and the other side may be attached to the inner bottom surface of the battery housing 142 by welding. The attachment structure between the second current collector 145 and the second uncoated portion 146b may be substantially the same as the attachment structure between the first current collector 144 and the first uncoated portion 146a.

The uncoated portions 146a, 146b are not limited to the structure shown in the figure. Therefore, the uncoated portions 146a, 146b may selectively have not only the structure of a conventional uncoated portion, but also the structure of the uncoated portion of the electrode according to the embodiment (variant form).

The insulator 146 can cover the first current collector 144. By covering the first current collector 144 with the upper surface of the first current collector 144, the insulator 146 can prevent direct contact between the first current collector 144 and the inner surface of the battery housing 142.

The insulator 146 has a lead hole 151 so that the lead 149 extending upward from the first collector 144 can be pulled out. The lead 149 is pulled out upward through the lead hole 151 and is coupled to the lower surface of the connecting plate 143c or the lower surface of the cap 143a.

The peripheral region of the insulator 146 may be interposed between the first current collector 144 and the beading portion 147 to fix the combination of the electrode assembly 141 and the first current collector 144. This limits the movement of the combination of the electrode assembly 141 and the first current collector 144 in the winding axis direction (Y-axis direction) of the cylindrical battery 140, thereby improving the assembly stability of the cylindrical battery 140.

The insulator 146 may be made of an insulating polymer resin. As an example, the insulator 146 may be made of polyethylene, polypropylene, polyimide, or polybutylene terephthalate.

The battery housing 142 may further include a vent portion 152 formed on the lower surface thereof. The vent portion 152 corresponds to a region on the lower surface of the battery housing 142 that is thinner than the surrounding region. The vent portion 152 is structurally weaker than the surrounding region. Therefore, if an abnormality occurs in the cylindrical battery 140 and the internal pressure increases above a certain level, the vent portion 152 may burst, allowing gas generated inside the battery housing 142 to be discharged to the outside. The internal pressure at which the vent portion 152 bursts may be about 15 kgf/ ^cm2 to 35 kgf/ ^cm2 .

The vent portion 152 may be formed in a continuous or discontinuous circular pattern on the underside of the battery housing 142. Alternatively, the vent portion 152 may be formed in a linear pattern or other patterns.

Figure 18 is a cross-sectional view of a cylindrical battery 150 according to another embodiment of the present invention, cut along the Y-axis direction.

Referring to FIG. 18, the cylindrical battery 150 is substantially the same as the cylindrical battery 140 of FIG. 17 except that the electrode structure of the second embodiment (variant) is adopted for the first uncoated portion 146a of the first electrode.

Referring to FIG. 18, the first uncoated portion 146a of the first electrode may have a shape in which the height of the second portion B3 decreases gradually or in steps toward the inner peripheral surface of the battery housing 142. Preferably, an imaginary line connecting the uppermost ends of the second portion B3 may have the same or similar shape as the inner peripheral surface of the beading portion 147.

The second part B3 forms an inclined surface. Therefore, when the battery housing 142 is pushed in to form the beading portion 147, the second part B3 can be prevented from being compressed and damaged by the beading portion 147. In addition, the phenomenon in which the second part B3 comes into contact with the battery housing 142 of the opposite polarity and causes an internal short circuit can be suppressed.

The rest of the configuration of the cylindrical battery 150 is substantially the same as the embodiment (variant) described above.

The uncoated portions 146a, 146b are not limited to the structure shown in the figure. Therefore, the uncoated portions 146a, 146b may selectively have not only the structure of a conventional uncoated portion, but also the structure of the uncoated portion of the electrode according to the embodiment (variant form).

Figure 19 is a cross-sectional view of a cylindrical battery 160 according to yet another embodiment of the present invention, cut along the Y-axis direction.

Referring to FIG. 19, the cylindrical battery 160 is substantially the same as the cylindrical batteries 140 and 150 described above, except that the lead 149 connected to the first collector 144 is directly connected to the cap 143a of the sealed body 143 through the lead hole 151 of the insulator 146, and the insulator 146 and the first collector 144 are in close contact with the underside of the cap 143a.

In the cylindrical battery 160, the diameter of the first current collector 144 and the outermost diameter of the third portion B2 are smaller than the smallest inner diameter of the battery housing 142. Also, the diameter of the first current collector 144 can be the same as or larger than the outermost diameter of the third portion B2.

Specifically, the minimum inner diameter of the battery housing 142 may correspond to the inner diameter of the battery housing 142 at the position where the beading portion 147 is formed. In this case, the outermost diameter of the first current collector 144 and the third portion B2 is smaller than the inner diameter of the battery housing 142 at the position where the beading portion 147 is formed. In addition, the diameter of the first current collector 144 may be the same as or larger than the outermost diameter of the third portion B2. The peripheral region of the insulator 146 is bent downward and interposed between the second portion B3 and the beading portion 147, and the combination of the electrode assembly 141 and the first current collector 144 can be fixed.

Preferably, the insulator 146 includes a portion covering the second portion B3 and a portion covering the first collector 144, and the portion connecting these two portions may have a shape that is bent together in accordance with the bent shape of the beading portion 147. The insulator 146 can insulate the second portion B3 from the inner circumferential surface of the beading portion 147, and at the same time, can insulate the first collector 144 from the inner circumferential surface of the beading portion 147.

The first current collector 144 may be located higher than the lower end of the beading portion 147 and may be coupled to the first part B1 and the third part B2. In this case, the pressing depth D1 of the beading portion 147 is smaller than or equal to the distance D2 from the inner peripheral surface of the battery housing 142 to the boundary between the second part B3 and the third part B2. Therefore, the first part B1 and the third part B2, and the first current collector 144 coupled thereto, may be located higher than the lower end of the beading portion 147. The lower end of the beading portion 147 refers to the bending point B between the part of the battery housing 142 in which the electrode assembly 141 is accommodated and the beading portion 147.

Since the first part B1 and the third part B2 occupy the radial inner space of the beading portion 147, the empty space between the electrode assembly 141 and the cap 143a is minimized. In addition, the connecting plate 143c that was located in the empty space between the electrode assembly 141 and the cap 143a is omitted. Therefore, the lead 149 of the first collector 144 can be directly connected to the lower surface of the cap 143a. With this structure, the empty space inside the battery is reduced, and the energy density can be maximized by the reduced empty space.

In the cylindrical battery 160, the first current collector 144 and the second current collector 145 can be welded to the ends of the first uncoated portion 146a and the second uncoated portion 146b, respectively, as in the above-described embodiment.

The uncoated portions 146a, 146b are not limited to the structure shown in the figure. Therefore, the uncoated portions 146a, 146b may selectively have not only the structure of a conventional uncoated portion, but also the structure of the uncoated portion of the electrode according to the embodiment (variant form).

Figure 20 is a cross-sectional view of a cylindrical battery 170 according to yet another embodiment of the present invention, cut along the Y-axis direction.

Referring to FIG. 20, the cylindrical battery 170 differs from the cylindrical battery 140 shown in FIG. 17 in that the electrode assembly structure is substantially the same, but other structures except for the electrode assembly have been changed.

Specifically, the cylindrical battery 170 includes a battery housing 171 through which a terminal 172 is inserted. The terminal 172 is attached through a through hole formed on the closed surface (top surface in the drawing) of the battery housing 171. The terminal 172 is riveted into the through hole of the battery housing 171 with a second gasket 173 made of an insulating material interposed therebetween. The terminal 172 is exposed to the outside in the direction opposite to the direction of gravity.

The terminal 172 includes a terminal exposure portion 172a and a terminal insertion portion 172b. The terminal exposure portion 172a is exposed to the outside of the closed surface of the battery housing 171. The terminal exposure portion 172a may be located in the approximate center of the closed surface of the battery housing 171. The maximum diameter of the terminal exposure portion 172a may be formed to be larger than the maximum diameter of the through hole formed in the battery housing 171. The terminal insertion portion 172b may penetrate the approximate center of the closed surface of the battery housing 171 and be electrically connected to the first uncoated portion 146a of the first electrode. The bottom periphery of the terminal insertion portion 172b may be riveted onto the inner surface of the battery housing 171. That is, the bottom periphery of the terminal insertion portion 172b may have a shape bent toward the inner surface of the battery housing 171. The inner side of the bottom periphery of the terminal insertion portion 172b includes a flat portion 172c. The maximum diameter of the bottom of the riveted terminal insertion portion 172b can be even larger than the maximum diameter of the through hole in the battery housing 171.

The flat portion 172c of the terminal insertion portion 172b may be welded to the center of the first current collector 144 connected to the first uncoated portion 146a of the first electrode. Laser welding is a preferred welding method, but other welding methods such as ultrasonic welding may be used instead.

An insulator 174 made of an insulating material may be interposed between the first collector 144 and the inner surface of the battery housing 171. The insulator 174 covers the upper portion of the first collector 144 and the upper peripheral portion of the electrode assembly 141. This prevents the second portion B3 of the electrode assembly 141 from coming into contact with the inner surface of the battery housing 171, which has the opposite polarity, causing a short circuit.

The thickness of the insulator 174 corresponds to or is slightly greater than the distance between the top surface of the first current collector 144 and the inner surface of the closed portion of the battery housing 171. Thus, the insulator 174 can contact the top surface of the first current collector 144 and the inner surface of the closed portion of the battery housing 171.

The terminal insert 172b of the terminal 172 can be welded to the first current collector 144 through a through hole in the insulator 174. The diameter of the through hole formed in the insulator 174 can be larger than the diameter of the rivet portion at the bottom of the terminal insert 172b. Preferably, the through hole can expose the bottom of the terminal insert 172b and the second gasket 173.

The second gasket 173 is interposed between the battery housing 171 and the terminal 172, and prevents electrical contact between the battery housing 171 and the terminal 172, which have opposite polarity. This allows the upper surface of the battery housing 171, which has a substantially flat shape, to function as a second electrode terminal (e.g., negative electrode) of the cylindrical battery 170.

The second gasket 173 includes a gasket exposure portion 173a and a gasket insertion portion 173b. The gasket exposure portion 173a is interposed between the terminal exposure portion 172a of the terminal 172 and the battery housing 171. The gasket insertion portion 173b is interposed between the terminal insertion portion 172b of the terminal 172 and the battery housing 171. The gasket insertion portion 173b may be deformed together with the terminal insertion portion 172b when the terminal insertion portion 172b is riveted, and may be closely attached to the inner surface of the battery housing 171. The second gasket 173 may be made of, for example, a polymer resin having insulating properties.

The gasket exposed portion 173a of the second gasket 173 may extend to cover the outer peripheral surface of the terminal exposed portion 172a of the terminal 172. When the second gasket 173 covers the outer peripheral surface of the terminal 172, it is possible to prevent a short circuit from occurring during the process of connecting an electrical connection component such as a bus bar to the upper surface of the battery housing 171 and/or the terminal 172. Although not shown, the gasket exposed portion 173a may extend to cover not only the outer peripheral surface of the terminal exposed portion 172a but also a portion of the upper surface.

When the second gasket 173 is made of a polymeric resin, the second gasket 173 may be joined to the battery housing 171 and the terminal 172 by thermal fusion. In this case, the airtightness at the joining interface between the second gasket 173 and the terminal 172 and at the joining interface between the second gasket 173 and the battery housing 171 is strengthened. On the other hand, when the gasket exposed portion 173a of the second gasket 173 has a shape that extends to the upper surface of the terminal exposed portion 172a, the terminal 172 may be integrally joined to the second gasket 173 by insert injection molding.

On the upper surface of the battery housing 171, the remaining area 175 excluding the area occupied by the terminal 172 and the second gasket 173 corresponds to a second electrode terminal having the opposite polarity to the terminal 172.

The second current collector 176 is coupled to the lower part of the electrode assembly 141. The second current collector 176 is made of a conductive metal material such as aluminum, steel, copper, or nickel, and is electrically connected to the second uncoated portion 146b of the second electrode.

Preferably, the second current collector 176 is electrically connected to the battery housing 171. Therefore, the second current collector 176 can be fixed with at least a portion of its peripheral portion interposed between the inner surface of the battery housing 171 and the first gasket 178b. As an example, at least a portion of the peripheral portion of the second current collector 176 can be fixed to the beading portion 180 by welding while being supported by the lower end surface of the beading portion 180 formed at the lower end of the battery housing 171. In a modified example, at least a portion of the peripheral portion of the second current collector 176 can be directly welded to the inner wall surface of the battery housing 171.

The second current collector 176 may have a plurality of projections and recesses (not shown) formed radially on the surface facing the second uncoated portion 146b. When projections and recesses are formed, the second current collector 176 may be pressed against the second uncoated portion 146b to press the projections and recesses into the projections and recesses.

Preferably, the second current collector 176 and the end of the second uncoated portion 146b may be joined by welding, for example, laser welding. In addition, the welded portion between the second current collector 176 and the second uncoated portion 146b may be spaced a predetermined distance from the inner circumferential surface of the beading portion 180 toward the core C.

The sealing body 178 that seals the lower open end of the battery housing 171 includes a plate-shaped cap 178a and a first gasket 178b. The first gasket 178b electrically separates the cap 178a from the battery housing 171. The crimping portion 181 fixes the periphery of the cap 178a and the first gasket 178b together. The cap 178a is provided with a vent portion 179. The configuration of the vent portion 179 is substantially the same as that of the above-mentioned embodiment (variant). The lower surface of the cap 178a may be located above the lower end of the crimping portion 181. In this case, a space is formed under the cap 178a, allowing for smooth venting. This is particularly useful when the cylindrical battery 170 is installed so that the crimping portion 181 faces the direction of gravity.

Preferably, the cap 178a is made of a metal material having electrical conductivity. However, since the first gasket 178b is interposed between the cap 178a and the battery housing 171, the cap 178a does not have electrical polarity. The seal 178 seals the open end of the lower part of the battery housing 171 and mainly functions to discharge gas when the internal pressure of the battery 170 increases above a critical value. The critical value of the internal pressure is 15 kgf/ ^cm2 to 35 kgf/ ^cm2 .

Preferably, the terminal 172 electrically connected to the first uncoated portion 146a of the first electrode is used as the first electrode terminal. Also, the portion 175 of the upper surface of the battery housing 171 electrically connected to the second uncoated portion 146b of the second electrode through the second collector 176, excluding the terminal 172, is used as the second electrode terminal of the opposite polarity to the first electrode terminal. In this way, when the two electrode terminals are located at the top of the cylindrical battery 170, it is possible to arrange electrical connection parts such as bus bars only on one side of the cylindrical battery 170. This can simplify the battery pack structure and improve the energy density. Also, since the portion 175 used as the second electrode terminal has a substantially flat shape, it is possible to secure a connection area sufficient for connecting electrical connection parts such as bus bars. As a result, the cylindrical battery 170 can reduce the resistance at the joint of the electrical connection parts to a preferable level.

Meanwhile, the structure of the electrode assembly 141 and the structure of the uncoated portion are not limited to those shown in the figures, and can be replaced with the structures of the above-mentioned embodiments (variations).

Figure 21 is a cross-sectional view of a cylindrical battery 180 according to yet another embodiment of the present invention, cut along the Y-axis direction.

Referring to FIG. 21, the cylindrical battery 180 has a structure of the electrode assembly 141 that is substantially the same as that of the cylindrical battery 150 shown in FIG. 18, and the other configurations except for the electrode assembly 141 are substantially the same as that of the cylindrical battery 170 shown in FIG. 20.

Therefore, the configurations of the embodiments (variations) of cylindrical batteries 150 and 170 can be similarly applied to cylindrical battery 180.

In addition, the structure of the electrode assembly 141 and the structure of the uncoated portion are not limited to those shown in the figures, and can be replaced with the structures of the above-mentioned embodiments (variations).

Figure 22 is a cross-sectional view of a cylindrical battery 190 according to yet another embodiment of the present invention, cut along the Y-axis direction.

Referring to FIG. 22, the cylindrical battery 190 includes the electrode assembly 110 shown in FIG. 14, and the other configurations except for the electrode assembly 110 are substantially the same as the cylindrical battery 140 shown in FIG. 17. Therefore, the configurations described with reference to FIGS. 14 and 17 can be applied substantially in the same manner in this embodiment.

Referring to FIG. 10a and FIG. 22, the first uncoated portion 146a and the second uncoated portion 146b of the electrode assembly 110 are folded in the radial direction of the electrode assembly 110, for example, from the outer periphery side to the core side, to form a folded surface region F.

The first part B1 is shorter than the other parts and corresponds to the segment-omitted section a1 where no segment exists, so it cannot be bent toward the core.

Preferably, the folded surface region F may include a section a1 where the segment is omitted, a section a2 where the segment height is variable, and a section a3 where the segment height is uniform, from the core side to the outer periphery.

As shown in Figures 10c, 10d, and 10e, the folded surface region F includes a uniform stacking number section b1 adjacent to the segment-free section a1, in which the number of segment stacks is 10 or more.

The folded surface region F may also include a layer count decreasing section b2 adjacent to the outer periphery of the electrode assembly 110, in which the number of layers of the segment decreases toward the outer periphery. Preferably, the layer count uniform section b1 may be set as a welding target region.

In the folded surface region F, the ratio (a2/c) of the height variable section a2 to the radius region (c) including the segment, the ratio (b1/c) of the uniform number of layers section b1 to the radius region (c) including the segment, and the ratio of the area of the uniform number of layers section b1 to the area of the folded surface region F have been described above, so repeated explanations will be omitted.

The first current collector 144 may be laser welded to the folded surface area F of the first uncoated portion 146a, and the second current collector 145 may be laser welded to the folded surface area F of the second uncoated portion 146b. The welding method may be ultrasonic welding, resistance welding, spot welding, or the like.

Preferably, 50% or more of the welding area W of the first current collector 144 and the second current collector 145 may overlap with the uniform lamination number section b1 of the folded surface area F. Alternatively, the remaining area of the welding area W may overlap with the reduced lamination number section b2 of the folded surface area F. It is more preferable that the entire welding area W overlaps with the uniform lamination number section b1 in terms of high welding strength, low resistance at the welding interface, and prevention of damage to the separation membrane and active material layer.

Preferably, in the uniform layer count section b1 that overlaps with the welding area W, and optionally in the reduced layer count section b2, the number of layers of the divided pieces may be 10 to 35.

Optionally, if the number of layers of the divided piece in the reduced number of layers section b2 that overlaps with the welding area W is less than 10, the laser output for welding the reduced number of layers section b2 can be lower than the laser output for welding the uniform number of layers section b1. In other words, if the welding area W overlaps with the uniform number of layers section b1 and the reduced number of layers section b2 at the same time, the laser output can be changed according to the number of layers of the divided piece. In this case, the welding strength of the uniform number of layers section b1 can be greater than the welding strength of the reduced number of layers section b2.

In the folded surface region F formed on the upper and lower parts of the electrode assembly 110, the radial lengths of the segment-omitted section a1 and/or the segment-height-variable section a2 and/or the segment-height-uniform section a3 may be the same or different.

In the electrode assembly 110, the height of the first portion B1 is relatively lower than the other portions. Also, as shown in FIG. 14, the bend length H of the innermost uncoated portion in the third portion B2 is smaller than the sum of the radial length R of the first portion B1 and 10% of the radius of the core 112.

Therefore, even if the first uncoated portion 146a is bent toward the core side, 90% or more of the diameter of the core 112 of the electrode assembly 110 can be opened to the outside. If the core 112 is not blocked, the electrolyte injection process is not hindered and the efficiency of the electrolyte injection is improved. In addition, the welding process between the second current collector 145 and the battery housing 142 can be easily performed by inserting a welding jig through the core 112.

When the uncoated portions 146a, 146b have a divided structure, if the width and/or height and/or spacing pitch of the divided pieces are adjusted to satisfy the numerical range of the above-mentioned embodiment, when the divided pieces are folded, the divided pieces overlap each other to an extent that sufficient welding strength is ensured, and no open space (gap) is formed in the folded surface area F.

Preferably, the first current collector 144 and the second current collector 145 may have an outer diameter that covers the end of the folded segment (see 61, 61' in FIG. 10f) at the last winding turn of the uniform height section a3 of the first electrode and the second electrode. In this case, the folded segment forming the folded surface region F can be welded in a state where it is uniformly pressed by the current collector, and the tightly stacked state of the segment can be maintained even after welding. A tightly stacked state means a state where there is substantially no gap between the segment segments, as shown in FIG. 10a. The tightly stacked state contributes to reducing the resistance of the cylindrical battery 190 to a level suitable for fast charging (e.g., 4 mΩ) or less.

The structure of the plain portions 146a and 146b may be changed to the structure according to the above-described embodiment (variation). In addition, there is no restriction on applying the conventional structure of a plain portion to either one of the plain portions 146a and 146b.

Figure 23 is a cross-sectional view of a cylindrical battery 200 according to yet another embodiment of the present invention, cut along the Y-axis direction.

Referring to FIG. 23, the cylindrical battery 200 includes the electrode assembly 110 shown in FIG. 14, and the other configurations except for the electrode assembly 110 are substantially the same as the cylindrical battery 180 shown in FIG. 21. Therefore, the configurations described with reference to FIGS. 14 and 21 can be applied substantially in the same manner to this embodiment.

Referring to FIG. 10a and FIG. 23, the first uncoated portion 146a and the second uncoated portion 146b of the electrode assembly 110 are folded in the radial direction of the electrode assembly 110, for example, from the outer periphery side to the core side, to form a folded surface region F.

The first part B1 is shorter than the other parts and corresponds to the segment-omitted section a1 where no segment exists, so it cannot be bent toward the core.

Preferably, the folded surface region F may include a section a1 where the segment is omitted, a section a2 where the segment height is variable, and a section a3 where the segment height is uniform, from the core side to the outer periphery.

As shown in Figures 10c, 10d, and 10e, the folded surface region F includes a uniform stacking number section b1 adjacent to the segment-free section a1, in which the number of segment stacks is 10 or more.

The folded surface region F may also include a layer count decreasing section b2 adjacent to the outer periphery of the electrode assembly 110, in which the number of layers of the segment decreases toward the outer periphery. Preferably, the layer count uniform section b1 may be set as a welding target region.

In the folded surface region F, the ratio (a2/c) of the height variable section a2 to the radius region (c) including the segment, the ratio (b1/c) of the uniform number of layers section b1 to the radius region (c) including the segment, and the ratio of the area of the uniform number of layers section b1 to the area of the folded surface region F have been described above, so repeated explanations will be omitted.

The first current collector 144 may be laser welded to the folded surface area F of the first uncoated portion 146a, and the second current collector 176 may be laser welded to the folded surface area F of the second uncoated portion 146b. The welding method may be ultrasonic welding, resistance welding, spot welding, or the like. The weld area W between the second current collector 176 and the second uncoated portion 146b may be spaced a predetermined distance from the inner surface of the beading portion 180.

Preferably, 50% or more of the welding area W of the first current collector 144 and the second current collector 176 may overlap with the uniform lamination number section b1 of the folded surface area F. Optionally, the remaining area of the welding area W may overlap with the reduced lamination number section b2 of the folded surface area F. It is more preferable that the entire welding area W overlaps with the uniform lamination number section b1 in terms of high welding strength, low resistance at the welding interface, and prevention of damage to the separation membrane and active material layer.

Preferably, in the uniform layer count section b1 that overlaps with the welding area W, and optionally in the reduced layer count section b2, the number of layers of the divided pieces may be 10 to 35.

Optionally, if the number of layers of the divided piece in the reduced number of layers section b2 that overlaps with the welding area W is less than 10, the laser output for welding the reduced number of layers section b2 may be lower than the laser output for welding the uniform number of layers section b1. That is, if the welding area W overlaps with the uniform number of layers section b1 and the reduced number of layers section b2 at the same time, the laser output may be changed according to the number of layers of the divided piece. In this case, the welding strength of the uniform number of layers section b1 may be greater than the welding strength of the reduced number of layers section b2.

In the folded surface region F formed on the upper and lower parts of the electrode assembly 110, the radial lengths of the segment-omitted section a1 and/or the segment-height-variable section a2 and/or the segment-height-uniform section a3 may be the same or different from each other.

In the electrode assembly 110, the height of the first portion B1 is relatively lower than the other portions. Also, as shown in FIG. 14, the bend length H of the innermost uncoated portion in the third portion B2 is smaller than the sum of the radial length R of the first portion B1 and 10% of the radius of the core 112.

Therefore, even if the first uncoated portion 146a is bent toward the core side, 90% or more of the diameter of the core 112 of the electrode assembly 110 can be opened to the outside. If the core 112 is not blocked, the electrolyte injection process is not hindered and the efficiency of the electrolyte injection is improved. In addition, the welding process between the first current collector 144 and the terminal 172 can be easily performed by inserting a welding jig through the core 112.

When the first uncoated portion 146a and the second uncoated portion 146b have a divided structure, if the width and/or height and/or spacing pitch of the divided pieces are adjusted to satisfy the numerical range of the above-mentioned embodiment, when the divided pieces are folded, the divided pieces overlap each other to an extent that sufficient welding strength is ensured, and no open space (gap) is formed in the folded surface area F.

Preferably, the first current collector 144 and the second current collector 176 may have an outer diameter such that the area in contact with the first uncoated portion 146a and the second uncoated portion 146b covers the end of the segment (see 61, 61' in FIG. 10f) folded at the last winding turn of the uniform height section a3 of the first electrode and the second electrode. In this case, the segment forming the folded surface region F can be welded in a state where it is uniformly pressed by the current collector, and the segment can be maintained in a tightly stacked state even after welding. A tightly stacked state means a state in which there is substantially no gap between the segment segments, as shown in FIG. 10a. The tightly stacked state contributes to reducing the resistance of the cylindrical battery 200 to a level suitable for fast charging (e.g., 4 mΩ) or less.

The structure of the plain portions 146a and 146b may be changed to the structure according to the above-described embodiment (variation). In addition, there is no restriction on applying the conventional structure of a plain portion to either one of the plain portions 146a and 146b.

Figure 24 is a cross-sectional view of a cylindrical battery 210 according to yet another embodiment of the present invention, cut along the Y-axis direction.

Referring to FIG. 24, the cylindrical battery 210 includes the electrode assembly 100 shown in FIG. 13, and the other configurations except for the electrode assembly 100 are substantially the same as the cylindrical battery 140 shown in FIG. 17. Therefore, the configurations described with reference to FIGS. 13 and 17 can be applied substantially in the same manner in this embodiment.

Preferably, the first uncoated portion 146a and the second uncoated portion 146b of the electrode assembly 100 are divided into a plurality of segments, and the plurality of segments are folded in the radial direction of the electrode assembly 100, for example, from the outer periphery side to the core side. At this time, the first portion B1 and the second portion B3 of the first uncoated portion 146a are lower in height than the other portions and do not include any segments, so they are not actually folded. The same is true for the second uncoated portion 146b.

In this embodiment, the folded surface region F may also include a segment-omitted section a1, a segment-height variable section a2, and a segment-height uniform section a3 from the core side to the outer periphery. However, because the second portion B3 is not folded, the radial length of the folded surface region F may be shorter than in the above-described embodiment.

As shown in Figures 10c, 10d, and 10e, the folded surface region F includes a uniform stacking number section b1 adjacent to the segment-free section a1, in which the number of segment stacks is 10 or more.

The folded surface region F may also include a layer count decreasing section b2 adjacent to the second portion B3 of the electrode assembly 110, in which the number of layers of the segment decreases toward the outer periphery. Preferably, the layer count uniform section b1 may be set as a welding target region.

In the folded surface region F, the ratio (a2/c) of the height variable section a2 to the radius region (c) including the segment, the ratio (b1/c) of the uniform number of layers section b1 to the radius region (c) including the segment, and the ratio of the area of the uniform number of layers section b1 to the area of the folded surface region F have been described above, so repeated explanations will be omitted.

The first current collector 144 may be welded to the folded surface area F of the first uncoated portion 146a, and the second current collector 145 may be welded to the folded surface area F of the second uncoated portion 146b.

The overlapping relationship between the uniform layer count section b1 and the reduced layer count section b2 and the welding area W, the outer diameters of the first current collector 144 and the second current collector 145, and the configuration in which the first portion B1 does not occlude more than 10% of the core diameter are substantially as described above.

On the other hand, the second part B3 does not include a split piece and has a height lower than the third part B2. Therefore, when the first plain portion 146a is bent, the second part B3 is not substantially bent. In addition, since the second part B3 is sufficiently separated from the beading portion 147, the problem of the second part B3 being damaged when the beading portion 147 is pressed in can be solved.

The structure of the plain portions 146a and 146b may be changed to the structure according to the above-described embodiment (variation). In addition, there is no restriction on applying the conventional structure of a plain portion to either one of the plain portions 146a and 146b.

Figure 25 is a cross-sectional view of a cylindrical battery 220 according to yet another embodiment of the present invention, cut along the Y-axis direction.

Referring to FIG. 25, the cylindrical battery 220 includes the electrode assembly 100 shown in FIG. 24, and the other configurations except for the electrode assembly 100 are substantially the same as the cylindrical battery 180 shown in FIG. 21. Therefore, the configurations described with reference to FIGS. 21 and 24 can be substantially similarly applied to this embodiment.

Preferably, the first uncoated portion 146a and the second uncoated portion 146b of the electrode assembly 100 are divided into a plurality of segments and are bent from the outer periphery toward the core. At this time, the first portion B1 and the second portion B3 of the first uncoated portion 146a are lower in height than the other portions and do not include a segment structure, so they are not actually bent toward the core. The same is true for the second uncoated portion 146b.

Therefore, in this embodiment, as in the embodiment of FIG. 24, the folded surface region F may include a segment-omitted section a1, a segment-height variable section a2, and a segment-height uniform section a3 from the core side to the outer periphery. However, because the second portion B3 is not folded, the radial length of the folded surface region F may be shorter than in the above-described embodiment.

As shown in Figures 10c, 10d, and 10e, the folded surface region F includes a uniform stacking number section b1 adjacent to the segment-free section a1, in which the number of segment stacks is 10 or more.

The folded surface region F may also include a layer count decreasing section b2 adjacent to the second portion B3 of the electrode assembly 110, in which the number of layers of the segment decreases toward the outer periphery. Preferably, the layer count uniform section b1 may be set as a welding target region.

In the folded surface region F, the ratio (a2/c) of the height variable section a2 to the radius region (c) including the segment, the ratio (b1/c) of the uniform number of layers section b1 to the radius region (c) including the segment, and the ratio of the area of the uniform number of layers section b1 to the area of the folded surface region F have been described above, so repeated explanations will be omitted.

The first current collector 144 may be welded to the folded surface area F of the first uncoated portion 146a, and the second current collector 176 may be welded to the folded surface area F of the second uncoated portion 146b.

The overlapping relationship between the uniform layer count section b1 and the reduced layer count section b2 and the welding area W, the outer diameters of the first current collector 144 and the second current collector 176, and the configuration in which the first portion B1 does not occlude more than 10% of the core diameter are substantially as described above.

The structure of the plain portions 146a and 146b may be changed to the structure according to the above-described embodiment (variation). In addition, there is no restriction on applying the conventional structure of a plain portion to either one of the plain portions 146a and 146b.

In the above-described embodiment (variant), the first current collector 144 and the second current collector 176 included in the cylindrical battery 170, 180, 200, 220 including the terminal 172 may have an improved structure as shown in Figures 26 and 27.

The improved structure of the first current collector 144 and the second current collector 176 can contribute to improving the vibration resistance and energy density while reducing the resistance of the cylindrical battery. In particular, the first current collector 144 and the second current collector 176 are effective when applied to a large cylindrical battery with a height-to-diameter ratio of greater than 0.4.

Figure 26 is a top view showing the structure of the first current collector 144 according to an embodiment of the present invention.

23 and 26, the first current collector 144 may include a peripheral portion 144a, a first non-coating portion coupling portion 144b, and a terminal coupling portion 144c. The peripheral portion 144a is disposed on the upper portion of the electrode assembly 110. The peripheral portion 144a may have an approximately rim shape with an open inner space S _open therein. Although the drawings show only a case where the peripheral portion 144a has an approximately circular rim shape, the present invention is not limited thereto. Unlike the drawings, the peripheral portion 144a may have an approximately square rim shape, a hexagonal rim shape, an octagonal rim shape, or other rim shapes. The number of the peripheral portions 144a may be increased to two or more. In this case, another peripheral portion having a rim shape may be included inside the peripheral portion 144a.

The terminal coupling portion 144c may have a diameter equal to or larger than the diameter of the flat portion 172c formed on the bottom surface of the terminal 172 to ensure a welding area for coupling with the flat portion 172c formed on the bottom surface of the terminal 172.

The first uncoated portion coupling portion 144b extends inward from the peripheral portion 144a and is coupled to the first uncoated portion 146a by welding. The terminal coupling portion 144c is spaced apart from the first uncoated portion coupling portion 144b and is positioned inside the peripheral portion 144a. The terminal coupling portion 144c may be coupled to a terminal 172 by welding. The terminal coupling portion 144c may be positioned, for example, at a substantially central portion of an inner space S _open surrounded by the peripheral portion 144a. The terminal coupling portion 144c may be provided at a position corresponding to a hole formed in the core C of the electrode assembly 110. The terminal coupling portion 144c may be configured to cover a hole formed in the core C of the electrode assembly 110 so that the hole formed in the core C of the electrode assembly 110 is not exposed to the outside of the terminal coupling portion 144c. Therefore, the terminal coupling portion 144 c may have a diameter or width larger than the hole formed in the core C of the electrode assembly 110 .

The first non-coated portion coupling portion 144b and the terminal coupling portion 144c may be disposed apart from each other and indirectly coupled to each other through the peripheral portion 144a. In this manner, the first current collector 144 has a structure in which the first non-coated portion coupling portion 144b and the terminal coupling portion 144c are not directly coupled to each other but are coupled to each other through the peripheral portion 144a. When the cylindrical battery 200 is subjected to shock and/or vibration, the shock applied to the coupling portion between the first non-coated portion coupling portion 144b and the first non-coated portion 146a and the coupling portion between the terminal coupling portion 144c and the terminal 172 may be dispersed. Although four first non-coated portion coupling portions 144b are shown in the drawings, the present invention is not limited thereto. The number of the first non-coated portion coupling portions 144b may be determined in various ways in consideration of the difficulty of manufacturing due to the complexity of the shape, the electrical resistance, the inner space S _open of the peripheral portion 144a in consideration of electrolyte impregnation, and the like.

The first collector 144 may further include a bridge portion 144d extending inward from the peripheral portion 144a and connected to the terminal coupling portion 144c. The bridge portion 144d may have at least a portion of a cross-sectional area smaller than the first non-coating portion coupling portion 144b and the peripheral portion 144a. For example, the bridge portion 144d may have at least a portion of a width and/or thickness smaller than the first non-coating portion coupling portion 144b. In this case, electrical resistance increases in the bridge portion 144d. As a result, when a current flows through the bridge portion 144d, the relatively large resistance causes a part of the bridge portion 144d to melt due to overcurrent heating, which irreversibly cuts off the overcurrent. The bridge portion 144d may have a cross-sectional area adjusted to an appropriate level in consideration of such an overcurrent cut-off function.

The bridge portion 144d may have a tapered portion 144e whose width gradually narrows from the inner surface of the peripheral portion 144a toward the terminal coupling portion 144c. When the tapered portion 144e is provided, the rigidity of the part is improved at the connection portion between the bridge portion 144d and the peripheral portion 144a. When the tapered portion 144e is provided, in the manufacturing process of the cylindrical battery 200, for example, a transport device and/or a worker can grasp the tapered portion 144e to easily and safely transport the first collector 144 and/or the combination of the first collector 144 and the electrode assembly 110. That is, when the tapered portion 144e is provided, it is possible to prevent product defects caused by grasping the parts that are welded to other parts, such as the first non-coated portion coupling portion 144b and the terminal coupling portion 144c.

The first uncoated portion joining portion 144b may be provided in plurality. The first uncoated portion joining portions 144b may be disposed at equal intervals along the extension direction of the peripheral portion 144a. The extension lengths of the first uncoated portion joining portions 144b may be approximately equal to each other. The first uncoated portion joining portion 144b may be joined to the folded surface region F of the first uncoated portion 146a by laser welding. The welding may be replaced by ultrasonic welding, spot welding, etc.

The weld pattern 144f formed by welding the first uncoated portion joint portion 144b to the folded surface region F may have a structure extending along the radial direction of the electrode assembly 110. The weld pattern 144f may be an array of line patterns or dot patterns.

The welding pattern 144f corresponds to a welding region. Therefore, it is preferable that the welding pattern 144f overlaps with the uniform layer number section b1 of the folded surface region F by 50% or more. The welding pattern 144f that does not overlap with the uniform layer number section b1 may overlap with the reduced layer number section b2. More preferably, the entire welding pattern 144f may overlap with the uniform layer number section b1 of the folded surface region F. It is preferable that the uniform layer number section b1 and optionally the reduced layer number section b2 of the folded surface region F below the point where the welding pattern 144f is formed have a number of layers of 10 or more in the divided pieces.

The terminal coupling portion 144c may be disposed so as to be surrounded by the first uncoated coupling portions 144b. The terminal coupling portion 144c may be coupled to the flat portion 172c of the terminal 172 by welding. The bridge portion 144d may be located between a pair of adjacent first uncoated coupling portions 144b. In this case, the distance from the bridge portion 144d to one of the pair of first uncoated coupling portions 144b along the extension direction of the peripheral portion 144a may be substantially the same as the distance from the bridge portion 144d to the other of the pair of first uncoated coupling portions 144b along the extension direction of the peripheral portion 144a. The cross-sectional area of each of the first uncoated coupling portions 144b may be substantially the same. The width and thickness of each of the first uncoated coupling portions 144b may be substantially the same.

Although not shown, a plurality of bridge portions 144d may be provided. Each of the bridge portions 144d may be disposed between an adjacent pair of first uncoated portion joining portions 144b. The bridge portions 144d may be disposed at substantially equal intervals from one another along the extension direction of the peripheral portion 144a. The distance from each of the bridge portions 144d to one of the adjacent pair of first uncoated portion joining portions 144b along the extension direction of the peripheral portion 144a may be substantially the same as the distance to the other first uncoated portion joining portion 144b.

As described above, when a plurality of first uncoated portion joining parts 144b and/or bridge parts 144d are provided, if the distance between the first uncoated portion joining parts 144b and/or the distance between the bridge parts 144d and/or the distance between the first uncoated portion joining parts 144b and the bridge part 144d are constant, a current can smoothly flow from the first uncoated portion joining parts 144b to the bridge part 144d or from the bridge part 144d to the first uncoated portion joining parts 144b.

The bridge portion 144d may include a notching portion N formed to partially reduce the cross-sectional area of the bridge portion 144d. The adjustment of the cross-sectional area of the notching portion N can be achieved, for example, by partially reducing the width and/or thickness of the bridge portion 144d. When the notching portion N is provided, the electrical resistance in the area where the notching portion N is formed increases, thereby enabling rapid current interruption when an overcurrent occurs.

The notch N is preferably provided in an area corresponding to the uniform number of layers section of the electrode assembly 110 to prevent foreign matter generated during breakage from entering the inside of the electrode assembly 110. This is because the number of layers of the segments of the first uncoated portion 146a is kept at a maximum in this area, allowing the overlapping segments to function as a mask.

The notch N can be wrapped with insulating tape. This prevents heat generated in the notch N from being dissipated to the outside, so that the notch N breaks more quickly when an overcurrent flows through the bridge portion 144d.

Figure 27 is a top view showing the structure of the second current collector 176 according to an embodiment of the present invention.

23 and 27, the second current collector 176 is disposed at the lower part of the electrode assembly 110. The second current collector 176 may be configured to electrically connect the uncoated portion 146b of the electrode assembly 110 to the battery housing 171. The second current collector 176 is made of a metal material having electrical conductivity and is electrically connected to the folded surface region F of the uncoated portion 146b. The second current collector 176 may be electrically connected to the battery housing 171. The second current collector 176 may be fixed by being interposed at its peripheral portion between the inner surface of the battery housing 171 and the first gasket 178b. Specifically, the second current collector 176 may be fixed at its peripheral portion between the lower surface of the beading portion 180 of the battery housing 171 and the first gasket 178b. However, this does not limit the present invention, and instead, the peripheral portion of the second current collector 176 may be welded to the inner wall surface of the battery housing 171 in an area where the beading portion 180 is not formed.

The second current collector 176 may include a support portion 176a disposed at the bottom of the electrode assembly 110, a second non-coated portion coupling portion 176b extending from the support portion 176a approximately along the radial direction of the electrode assembly 110 and coupled to the bent surface region F of the non-coated portion 146b, and a housing coupling portion 176c extending from the support portion 176a approximately inclined toward the inner surface of the battery housing 171 based on the radial direction of the electrode assembly 110 and coupled to the inner surface. The second non-coated portion coupling portion 176b and the housing coupling portion 176c are indirectly connected to each other through the support portion 176a and are not directly connected to each other. Therefore, when an external impact is applied to the cylindrical battery 200 according to one embodiment of the present invention, damage occurring to the coupling portion between the second current collector 176 and the electrode assembly 110 and the coupling portion between the second current collector 176 and the battery housing 171 can be minimized. However, the second current collector 176 according to an embodiment of the present invention is not limited to the case where the second non-coated portion coupling portion 176b and the housing coupling portion 176c are indirectly connected to each other. For example, the second current collector 176 may have a structure that does not include the support portion 176a that indirectly couples the second non-coated portion coupling portion 176b and the housing coupling portion 176c and/or a structure where the non-coated portion 146b and the housing coupling portion 176c are directly connected to each other.

The support portion 176a and the second plain portion joining portion 176b are disposed at the bottom of the electrode assembly 110. The second plain portion joining portion 176b is joined to the folded surface region F of the plain portion 146b. Not only the second plain portion joining portion 176b but also the support portion 176a may be joined to the plain portion 146b. The second plain portion joining portion 176b and the folded surface region F of the plain portion 146b may be joined by laser welding. The welding may be replaced by ultrasonic welding, spot welding, or the like. The support portion 176a and the second plain portion joining portion 176b are located above the beading portion 180 when the beading portion 180 is formed on the battery housing 171.

The support portion 176a has a collector hole 176d formed at a position corresponding to a hole formed in the core C of the electrode assembly 110. The core C of the electrode assembly 110 and the collector hole 176d, which are connected to each other, can function as a passage for inserting a welding rod for welding between the terminal 172 and the terminal coupling portion 144c of the first collector 144 or for irradiating a laser beam.

The current collector hole 176d may have a radius of 0.5r _c or more with respect to the radius r _c of the hole formed in the core C of the electrode assembly 110. When the radius of the current collector hole 176d is 0.5r _c to 1.0r _c , a phenomenon in which a separator or an electrode winding structure near the core C of the electrode assembly 110 is pushed out of the core C due to vent pressure when venting occurs in the cylindrical battery 200 is prevented. When the radius of the current collector hole 176d is greater than 1.0r _c , the core C is maximally opened, making it easier to inject the electrolyte in the electrolyte injection process.

When a plurality of the second uncoated portion joints 176b are provided, the second uncoated portion joints 176b may extend radially from the support portion 176a of the second current collector 176 toward the side wall of the battery housing 171. Each of the second uncoated portion joints 176b may be spaced apart from one another along the circumference of the support portion 176a.

The housing coupling portion 176c may be provided in a plurality of pieces. In this case, the plurality of housing coupling portions 176c may have a shape extending from the center of the second collector 176 toward the side wall of the battery housing 171 in a substantially radial manner. Thus, the electrical connection between the second collector 176 and the battery housing 171 may be performed at a plurality of points. By performing coupling for electrical connection at a plurality of points in this manner, the coupling area can be maximized and electrical resistance can be minimized. Each of the plurality of housing coupling portions 176c may be located apart from each other along the circumference of the support portion 176a. At least one housing coupling portion 176c may be located between adjacent second non-coating portion coupling portions 176b. The plurality of housing coupling portions 176c may be coupled to, for example, the beading portion 180 of the inner surface of the battery housing 171. The housing coupling portion 176c may be coupled to the lower surface of the beading portion 180, in particular, through laser welding. Welding may be replaced with ultrasonic welding, spot welding, or the like. By welding a plurality of housing coupling parts 176c onto the beading part 180 in this way, the current path can be dispersed radially, limiting the resistance level of the cylindrical battery 200 to about 4 mΩ or less. In addition, the lower surface of the beading part 180 is formed to extend in a direction approximately parallel to the upper surface of the battery housing 171, i.e., in a direction approximately perpendicular to the side wall of the battery housing 171, and the housing coupling parts 176c are also formed to extend in the same direction, i.e., in the radial and circumferential directions, so that the housing coupling parts 176c can be stably contacted onto the beading part 180. In addition, as the housing coupling parts 176c are stably contacted onto the flat part of the beading part 180 in this way, the welding between the two parts is smoothly performed, thereby improving the bonding strength between the two parts and minimizing the increase in resistance at the bonding site.

The housing coupling portion 176c may include a contact portion 176e that is coupled to the inner surface of the battery housing 171, and a coupling portion 176f that connects between the support portion 176a and the contact portion 176e.

The contact portion 176e is coupled to the inner surface of the battery housing 171. When the beading portion 180 is formed on the battery housing 171, the contact portion 176e may be coupled to the beading portion 180 as described above. More specifically, the contact portion 176e may be electrically connected to a flat portion formed on the lower surface of the beading portion 180 formed on the battery housing 171, and may be interposed between the lower surface of the beading portion 180 and the first gasket 178b. In this case, for stable contact and coupling, the contact portion 176e may have a shape that extends a predetermined length along the circumferential direction of the battery housing 171 at the beading portion 180.

The connecting portion 176f may be bent at an obtuse angle. The bending point may be above the midpoint of the connecting portion 176f. When the connecting portion 176f is bent, the contact portion 176e is stably supported on the flat surface of the beading portion 180. The connecting portion 176f may be divided into a lower portion and an upper portion based on the bending point, and the length of the lower portion may be greater than that of the upper portion. Also, the inclination angle based on the surface of the support portion 176a may be greater at the lower portion of the bending point than at the upper portion. When the connecting portion 176f is bent, it is possible to buffer pressure (force) applied in the vertical direction of the battery housing 171. For example, when pressure is transmitted to the contact portion 176e during the sizing process of the battery housing 171 and the contact portion 176e moves vertically toward the support portion 176a, the bending point of the connecting portion 176f moves upward and the connecting portion 176f is deformed, thereby buffering stress.

Meanwhile, it is preferable that the maximum distance from the center of the second collector 176 to the end of the second uncoated portion joining portion 176b along the radial direction of the electrode assembly 110 is equal to or smaller than the inner diameter of the battery housing 171 in the region where the beading portion 180 is formed, i.e., the minimum inner diameter of the battery housing 171. This is to prevent the end of the second uncoated portion joining portion 176b from pressing against the periphery of the electrode assembly 110 during the sizing process in which the battery housing 171 is compressed along the height direction.

The second uncoated joint portion 176b includes holes 176g. The holes 176g can be used as a passage for electrolyte movement. The weld pattern 176h formed by welding the second uncoated joint portion 176b to the folded surface region F can have a structure extending along the radial direction of the electrode assembly 110. The weld pattern 176h can be an array of line patterns or dot patterns.

The welding pattern 176h corresponds to a welding region. Therefore, it is preferable that the welding pattern 176h overlaps with the uniform layer number section b1 of the folded surface region F located at the bottom of the electrode assembly 110 by 50% or more. The welding pattern 176h that does not overlap with the uniform layer number section b1 may overlap with the reduced layer number section b2. More preferably, the entire welding pattern 176h may overlap with the uniform layer number section b1 of the folded surface region F. It is preferable that the number of layers of the divided pieces is 10 or more in the uniform layer number section b1 and, optionally, the reduced layer number section b2 of the folded surface region F located above the point where the welding pattern 176h is formed.

The first current collector 144 and the second current collector 176 have different outer diameters. The outer diameter is the outer diameter of the outer end of the contact area between the folded surface area F and the current collector. The outer diameter is defined as the maximum value of the distance between the two points where a straight line passing through the center of the core C of the electrode assembly intersects with the end of the contact area. The second current collector 176 is located inside the beading portion 180, so its outer diameter is smaller than that of the first current collector 144. In addition, the length of the welding pattern 144f of the first current collector 144 is longer than the length of the welding pattern 176h of the second current collector 176. Preferably, the welding pattern 144f and the welding pattern 176h may extend from substantially the same point on the outer periphery with respect to the center of the core C.

The cylindrical batteries 170, 180, 200, and 220 according to embodiments of the present invention can have electrical connections at the top.

Figure 28 is a top view showing a state in which multiple cylindrical batteries 200 are electrically connected, and Figure 29 is a partially enlarged view of Figure 28. The cylindrical battery 200 can be replaced with cylindrical batteries 170, 180, 220 of other structures.

Referring to FIG. 28 and FIG. 29, a plurality of cylindrical batteries 200 can be connected in series and parallel at the top of the cylindrical batteries 200 using bus bars 210. The number of cylindrical batteries 200 can be increased or decreased depending on the capacity of the battery pack.

In each cylindrical battery 200, the terminal 172 may have a positive polarity and the flat surface 171a around the terminal 172 of the battery housing 171 may have a negative polarity. Of course, the opposite is also possible.

Preferably, the cylindrical batteries 200 may be arranged in a number of rows and columns. In the drawings, the rows are in the vertical direction and the rows are in the horizontal direction. In addition, to maximize space efficiency, the cylindrical batteries 200 may be arranged in a close packing structure. The close packing structure is formed when an equilateral triangle is drawn when the centers of the terminals 172 exposed to the outside of the battery housing 171 are connected to each other. Preferably, the bus bar 210 connects the cylindrical batteries 200 arranged in the same row in parallel with each other, and connects the cylindrical batteries 200 arranged in two adjacent rows in series.

Preferably, the busbar 210 may include a body portion 211, a plurality of first busbar terminals 212, and a plurality of second busbar terminals 213 for series and parallel connection.

The body portion 211 may extend along the row of cylindrical batteries 200 between adjacent terminals 172. Alternatively, the body portion 211 may extend along the row of cylindrical batteries 200 but be folded in a regular pattern, such as a zigzag pattern.

The first busbar terminals 212 may extend from one side of the body portion 211 and be electrically coupled to the terminals 172 of the cylindrical battery 200 located on one side. The electrical coupling between the first busbar terminals 212 and the terminals 172 may be performed by laser welding, ultrasonic welding, etc.

The second busbar terminals 213 may extend from the other side of the body portion 211 and be electrically connected to the flat surface 171a around the terminals 172 located on the other side. The electrical connection between the second busbar terminals 213 and the flat surface 171a may be performed by laser welding, ultrasonic welding, or the like.

Preferably, the body portion 211, the plurality of first busbar terminals 212, and the plurality of second busbar terminals 213 may be formed from a single conductive metal plate. The metal plate may be, for example, an aluminum plate or a copper plate, but the present invention is not limited thereto. As a variant, the body portion 211, the plurality of first busbar terminals 212, and the second busbar terminals 213 may be manufactured as separate pieces and then joined together by welding or the like.

The cylindrical battery 200 according to one embodiment of the present invention has a structure in which resistance is minimized by expanding the welding area through the folded surface region F, multiplying the current path using the second current collector 176, and minimizing the length of the current path. The AC resistance of the cylindrical battery 200 measured by a resistance meter between the positive and negative electrodes, i.e., between the terminal 172 and the surrounding flat surface 171a, may be 0.5 mΩ to 4 mΩ, and preferably 1 mΩ to 4 mΩ, which is suitable for fast charging.

In one embodiment of the present invention, the cylindrical battery 200 has a terminal 172 with a positive polarity and a flat surface 171a with a negative polarity positioned in the same direction, so that electrical connection between cylindrical batteries 200 can be easily achieved using a bus bar 210.

In addition, the terminal 172 of the cylindrical battery 200 and the surrounding flat surface 171a have a large area, so that the connection area of the bus bar 210 is sufficiently secured, and the resistance of the battery pack including the cylindrical battery 200 can be sufficiently reduced.

In addition, electrical wiring can be performed on the top of the cylindrical battery 200, maximizing the energy density per unit volume of the battery module/pack.

The cylindrical battery according to the above-described embodiment (variant) is used to manufacture a battery pack.

Figure 30 is a diagram showing the configuration of a battery pack according to one embodiment of the present invention.

Referring to FIG. 30, a battery pack 300 according to one embodiment of the present invention includes an assembly to which cylindrical batteries 301 are electrically connected, and a pack housing 302 that accommodates the cylindrical batteries. The cylindrical batteries 301 may be any one of the batteries according to the above-described embodiments (variants). For convenience of illustration, components such as bus bars, cooling units, and external terminals for electrical connection of the cylindrical batteries 301 are not shown.

The battery pack 300 is mounted on a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle may include a four-wheeled vehicle or a two-wheeled vehicle.

Figure 31 is a diagram illustrating a vehicle including the battery pack 300 of Figure 30.

Referring to FIG. 31, an automobile V according to one embodiment of the present invention includes a battery pack 300 according to one embodiment of the present invention. The automobile V operates by receiving power from the battery pack 300 according to one embodiment of the present invention.

According to one embodiment of the present invention, the uncoated portions protruding from the upper and lower sides of the electrode assembly themselves can be used as electrode tabs, thereby reducing the internal resistance of the battery and increasing the energy density.

In addition, according to one embodiment of the present invention, the structure of the uncoated portion of the electrode assembly is improved so that the electrode assembly does not interfere with the inner surface of the battery housing during the process of forming the beading portion of the battery housing, preventing an internal short circuit in a cylindrical battery due to partial deformation of the electrode assembly.

In addition, according to one embodiment of the present invention, the structure of the uncoated portion of the electrode assembly is improved to prevent the uncoated portion from tearing when it is bent, and the number of overlapping layers of the uncoated portion is sufficiently increased to improve the welding strength of the current collector.

Furthermore, according to one embodiment of the present invention, the segment groups can be arranged radially along the radial direction of the electrode assembly in a number of predefined regions by adjusting the spacing between the segment groups. In this case, the folded surface regions of the segment can be separated in the circumferential direction and the electrolyte can be impregnated through the regions between the folded surface regions, thereby improving the electrolyte impregnation speed.

In addition, according to one embodiment of the present invention, a segment structure is applied to the uncoated portion of the electrode, and the dimensions of the segments (width, height, and spacing pitch) are optimized to sufficiently increase the number of segments stacked in the area used as the welding target area, thereby improving the physical properties of the area where the current collector is welded.

In addition, according to one embodiment of the present invention, by applying a structure in which a current collector is welded over a wide area to the folded surface area formed by bending the divided pieces, it is possible to provide an electrode assembly with improved energy density and reduced resistance.

Furthermore, according to one embodiment of the present invention, a cylindrical battery with an improved design is provided that allows electrical wiring to be performed at the top.

In addition, according to one embodiment of the present invention, the structure of the uncoated portion adjacent to the core of the electrode assembly is improved to prevent the cavity in the core of the electrode assembly from being blocked when the uncoated portion is bent, facilitating the electrolyte injection process and the welding process between the battery housing (or terminal) and the current collector.

In addition, according to one embodiment of the present invention, it is possible to provide a cylindrical battery having a structure in which the internal resistance is low, internal short circuits are prevented, and the welding strength between the current collector and the uncoated portion is improved, as well as a battery pack and a vehicle including the cylindrical battery.

In particular, the present invention provides a cylindrical battery having a height-to-diameter ratio of 0.4 or more and a resistance of 4 mΩ or less, and a battery pack and a vehicle including the cylindrical battery.

As described above, the present invention has been described using limited embodiments and drawings, but the present invention is not limited thereto, and it goes without saying that various modifications and variations are possible within the scope of the technical concept of the present invention and the scope of the claims by a person having ordinary knowledge in the technical field to which the present invention pertains.

10 Positive electrode 10a Positive electrode uncoated portion 11 Negative electrode 11a Negative electrode uncoated portion 12 Separator 20 Current collector 21 Active material 22 Uncoated portion 30, 31 Current collector 32 Uncoated portion 33 Cavity 34 Peripheral region 40 Electrode 41 Current collector 42 Active material layer 43 Uncoated portion 44 Insulating layer 45 Electrode 50 Electrode 53b Side portion 60 Electrode 61 Segment 61g Segment alignment portion 63 Cut groove 63a Bottom 63b Side edge 63c Rounded portion 70 Electrode 80 Electrode assembly 81 End 90 Electrode assembly 91 End 92 Outermost portion 100 Electrode assembly 101 End 102 Core 110 Electrode assembly 111 End 112 Core 120 Electrode assembly 121 End 122 Core 130 Electrode assembly 131 End 132 Core 140 Cylindrical battery 141 Electrode assembly 142 Battery housing 143 Sealing body 143a Cap 143b First gasket 143c Connection plate 143d Protrusion 144 First current collector 144a Edge 144b First uncoated portion coupling portion 144c Terminal coupling portion 144d Bridge portion 144e Tapered portion 144f Welding pattern 145 Second current collector 146 Insulator 146a First uncoated portion 146a Uncoated portion 146b Second uncoated portion 146b Uncoated portion 147 Beading portion 148 Crimping portion 149 Lead 150 Cylindrical battery 151 Lead hole 152 Vent portion 160 Cylindrical battery 170 Cylindrical battery 171 Battery housing 171a Flat surface 172 Terminal 172a Terminal exposed portion 172b Terminal insertion portion 172c Flat portion 173 Second gasket 173a Gasket exposed portion 173b Gasket insertion portion 174 Insulator 175 Region 176 Second current collector 176a Support portion 176b Second uncoated portion coupling portion 176c Housing coupling portion 176d Current collector hole 176e Contact portion 176f Connection portion 176g Hole 176h Welding pattern 178 Sealing body 178a Cap 178b First gasket 179 Vent portion 180 Cylindrical battery 180 Beading portion 181 Crimping portion 190 Cylindrical battery 200 Cylindrical battery 210 Cylindrical battery 210 Busbar 211 Body portion 212 First busbar terminal 213 Second busbar terminal 220 Cylindrical battery 300 Battery pack 301 Cylindrical battery 302 Pack housing

Claims (36)

An electrode assembly in which a core and an outer circumferential surface are defined by winding a first electrode, a second electrode, and a separator interposed between the first electrode and the second electrode around a winding shaft,
The first electrode includes a first active material portion coated with an active material layer along a winding direction, and a first uncoated portion not coated with an active material layer,
The first uncoated portion includes a plurality of segment sections that are divided into a plurality of segment sections that can be independently folded by a plurality of cutting grooves provided along a winding direction,
The portion segment section includes a plurality of portion segment groups arranged at intervals between the groups along the winding direction,
one end surface of the electrode assembly includes a plurality of segment alignment portions in which the plurality of segment groups are aligned along a radial direction, and an electrolyte-impregnated portion in which an end of the first active material portion is exposed between adjacent segment alignment portions in a circumferential direction between the segment alignment portions, the end of the first active material portion being exposed between turns of a separator;
the segments included in the segment alignment portion are bent toward the core to form a bent surface region;
an end of the separation membrane is spaced apart from a reference line extending in a winding axis direction along positions corresponding to the plurality of cutting grooves by a predetermined distance or less;
The predetermined distance is 30% of a minimum height of segments forming the folded surface area. The electrode assembly of claim 1, wherein the folded surface area is fan-shaped. The electrode assembly according to claim 2, wherein the width in the winding direction of each segment group arranged in the folded surface region increases stepwise or gradually from the core side to the outer periphery side. The electrode assembly of claim 2, wherein the number of segments included in each segment group arranged in the folded surface region increases gradually or stepwise from the core side toward the outer periphery side. The electrode assembly of claim 1, wherein the segments included in the same segment group have the same one or more selected from the width in the winding direction, the height in the winding axial direction, the lower interior angle, and the spacing pitch in the winding direction. The electrode assembly of claim 1, wherein the segment included in the segment group located in the first winding turn is smaller than the segment included in the segment group located in the second winding turn located outside the first winding turn in one or more selected from the width in the winding direction, the height in the winding axis direction, the lower inner angle, and the separation pitch in the winding direction. The electrode assembly of claim 1, wherein one or more of the width in the winding direction, the height in the winding axial direction, the lower interior angle, and the separation pitch in the winding direction of the segments included in the segment groups located on different winding turns increases gradually or stepwise as the radius of the winding turn increases. The electrode assembly of claim 1, wherein the folded surface area has a rectangular, trapezoidal, or parallelogram shape. The electrode assembly of claim 1, wherein the folded surface area and the electrolyte-impregnated portion extend radially relative to the core. The electrode assembly according to claim 1, in which, when a line connecting the center of the core and the geometric center of a figure that approximately corresponds to the folded surface region is defined as an angle measurement line, the angles between the angle measurement lines of adjacent folded surface regions in the circumferential direction are approximately equal. The electrode assembly of claim 10, wherein the angle is substantially 30°, 40°, 45°, 60°, 72°, 90°, 120°, or 180°. The electrode assembly of claim 1, wherein at least some of the segment groups included in the segment alignment section are rotated clockwise or counterclockwise around the winding shaft as the radius of the winding turn increases. The electrode assembly of claim 12, wherein the amount of rotation of the segment group when rotated clockwise or counterclockwise about the winding shaft increases as the radius of the winding turn increases. an insulating layer covering a boundary area between the first non-coating portion and the active material layer along the winding direction,
The electrode assembly of claim 1 , wherein a gap is provided between the insulating layer and the kerf. The electrode assembly of claim 14, wherein the gap varies along the winding direction. The electrode assembly of claim 15, wherein the gap is increased or decreased in a predetermined region of the first electrode compared to other regions. The electrode assembly according to claim 15, wherein in a given region of the first electrode, the gap increases gradually or stepwise along a direction parallel to the winding direction. The electrode assembly of claim 14, wherein the gap is between 0.2 mm and 4 mm. The electrode assembly according to claim 14, wherein the insulating layer is exposed to the outside of the separator along the winding axis direction. The electrode assembly according to claim 15, wherein the insulating layer is thinner than the active material layer and is disposed apart from the separator. 2. The electrode assembly of claim 1, wherein the segment alignment portion includes a height variable section in which the height of the segment increases stepwise from a first height h ₁ to an N-1th height h _N-1 (N is a natural number greater than or equal to 3) from a core side to an outer periphery of the electrode assembly, and a height uniform section in which the height of the segment is uniformly maintained at an Nth height h _N (greater than h _N- 1). 22. The electrode assembly of claim 21, wherein when a starting radius of a winding turn including a segment having a height _hk (k is a natural number from 1 to N) is defined as _rk , 90% or more of the diameter of the core of the electrode assembly is not blocked by the bend of the segment located at _rk . When the starting radius of a winding turn including a segment having a height _hk (k is a natural number from 1 to N) is _rk and the radius of the core is _rc , the height _hk of the segment satisfies the following formula: 2mm≦ _hk ≦rk- _α × _rc (α is 0.90 to 1).
The electrode assembly of claim 21 , The electrode assembly according to claim 1, wherein the segment alignment section includes, in order along the radial direction based on a cross section along the winding axis, a segment-free section where no segments are present, a height-variable section where the height of the segments varies, and a height-uniform section where the height of the segments is uniform, and a plurality of the segment segments are arranged in the height-variable section and the height-uniform section. The electrode assembly according to claim 24, wherein the number of segments that intersect with a virtual line parallel to the winding axis direction at any radial position of the folded surface region with respect to the center of the core of the electrode assembly is defined as the number of layers of the segments at that radial position, and the folded surface region includes a uniform number of layers section in which the number of layers of the segments is uniform from the core side to the outer periphery, and a decreasing number of layers section located outside the uniform number of layers section in which the number of layers of the segments decreases toward the outer periphery. The electrode assembly according to claim 25, wherein the number of stacked segments in the uniform stacking section is 10 to 35. The electrode assembly of claim 25, wherein the first electrode is a positive electrode, and the lamination thickness of the divided pieces in the uniform lamination number section is 100 μm to 875 μm. The electrode assembly of claim 25, wherein the first electrode is a negative electrode, and the lamination thickness of the divided pieces in the uniform lamination number section is 50 μm to 700 μm. the second electrode includes a second active material portion coated with an active material layer along a winding direction, and a second uncoated portion not coated with an active material layer,
The second uncoated portion includes a section that is divided into a plurality of sections that can be bent independently by a plurality of cutting grooves provided along a winding direction,
The second non-coating portion includes a plurality of segment groups arranged at intervals along the winding direction,
the other end surface of the electrode assembly includes a plurality of segment alignment portions in which the plurality of segment groups of the second uncoated portion are aligned along a radial direction, and an electrolyte-impregnated portion in which an end of the second active material portion is exposed between the wound turns of a separator between the segment alignment portions of the second uncoated portion adjacent to each other in a circumferential direction,
the segments included in the segment alignment portion of the second uncoated portion are folded toward the core to form a folded surface region;
an end of the separation membrane is spaced apart from a reference line extending in a winding axis direction along positions corresponding to the plurality of cutting grooves of the second non-coating portion by a predetermined distance or less;
2. The electrode assembly of claim 1, wherein the predetermined distance is 30% of a minimum height of a segment of the second uncoated portion that forms the folded surface area. An electrode assembly in which a core and an outer circumferential surface are defined by winding a first electrode, a second electrode, and a separator interposed between the first electrode and the second electrode around a winding shaft, the first electrode including a first active material portion coated with an active material layer along a winding direction, and a first uncoated portion not coated with an active material layer, the first uncoated portion including a segment section divided into a plurality of segments that can be independently bent by a plurality of cutting grooves provided along the winding direction, the segment section including a plurality of segment groups arranged at intervals between the groups along the winding direction, an electrode assembly, wherein one side end surface of the assembly includes a plurality of segment alignment portions in which a plurality of the segment groups are aligned along a radial direction, and an electrolyte-impregnated portion between adjacent segment alignment portions in which an end of the first active material portion is exposed between the wound turns of a separator, the segment included in the segment alignment portion is folded toward the core to form a folded surface region, and an end of the separator is spaced apart from a reference line extending in a winding axis direction along positions corresponding to the plurality of cutting grooves within a predetermined distance, the predetermined distance being 30% of a minimum height of the segment forming the folded surface region;
a battery housing that houses the electrode assembly and is electrically connected to one of the first electrode and the second electrode and has a first polarity;
a seal for sealing an open end of the battery housing;
a terminal electrically connected to the other of the first electrode and the second electrode, the terminal having a surface exposed to the outside and a second polarity. a beading portion formed by pressing a peripheral area of an open end of the battery housing into the inside of the battery housing;
a current collector electrically coupled to the folded surface region;
The battery of claim 30 , further comprising an insulator covering the current collector and having a periphery interposed and fixed between the inner circumferential surface of the beading portion and the current collector. The electrode assembly has a core having a cavity therein,
31. The battery of claim 30, wherein the cavity is not blocked by the folded surface region and is open to the outside. the sealing body includes a cap that seals an open end of the battery housing, and a gasket that encloses a periphery of the cap and is crimped onto an upper end of the battery housing;
31. The battery of claim 30, wherein the terminal having the second polarity is the cap. a current collector electrically connected to the uncoated portion of the second electrode having the first polarity and having at least a portion of a periphery attached to a side wall of the battery housing;
the sealing body includes a non-polarized cap and a gasket crimped around a periphery of the cap to an upper end of the battery housing;
31. The battery of claim 30, wherein the battery housing includes a rivet terminal insulatively attached to a through hole formed in a central portion of the closed surface, electrically connected to the first electrode, and having the second polarity. A battery pack comprising a plurality of batteries according to any one of claims 30 to 34. A motor vehicle including the battery pack according to claim 35.